INCOME FROM SPORT BETTING

Having supported myself solely through sportsbetting (mostly on NFL football) for about a decade, and during that time interacting with a lot of folks on both sides of the counter who helped me learn what it takes to win, I can make several suggestions to the person serious about making money betting on sports:
1. Bet with your head, not your heart.
There are reasons-cold, hard, dry, dull, mathematical, boring, logical reasons-for or against any bet you could make. A good way to lose is to let your emotions sway you from such reasons.
Don't bet on a team because you grew up rooting for them. Don't bet a game because it's televised. Don't bet more on Monday Night Football because you want to catch back what you lost over the weekend (or because you want to go for the big kill after a winning weekend). Don't hedge a bet because you have a psychological preference for safety. Don't bet a game because you haven't found anything to bet all day and it's getting late and you really wanted to gamble today. Don't bet a "teaser" just because it's a "fun" way to bet. Etc., etc.
If that kills it for you because it sounds too much like a job, then accept that you're a "recreational" bettor, and not destined to make money at this.
2. Learn math.
Simple addition, multiplication, division, fractions, percentages, etc. will handle a lot of what you need to do. But the more knowledge you have of probability and statistics and more advanced areas like that, the more you'll find it opening up new opportunities for you and enabling you to better exploit existing opportunities.
3. Realize that it takes money to make money.
A lot of the factors I'll talk about below are easier to do the more money you have. People with $100,000 to invest in sportsbetting can pursue a lot more strategies a lot more effectively than people with $1,000 to invest.
4. Have as many sportsbetting accounts as you can handle.
If you're playing with the neighborhood bookie, making all your bets with just one person or shop, that eliminates or lessens almost all the ways you can make money sportsbetting. So I'm assuming you have legal access to online sportsbooks. If so, don't pick one or two and put all your action in there. Pick ten or twenty or thirty. (When you're playing online, it's not unrealistic to manage that many. It's not like we're talking about running around on foot to dozens of Vegas sportsbooks in person.)
5. Be careful to use only the safest sportsbooks.
Don't open an account at a sportsbook just because you got a mailer in your mailbox, or a spam e-mail, or saw a banner ad, or saw a link in an online article. Go to the various sportsbetting forums online and research which places people recommend. Then research them further through Google or other means, looking to see if you can find anyone claiming them to be a scam or pulling anything underhanded. Call them and make sure you're comfortable with them before committing. After you join, keep your eyes open for further news on the forums and elsewhere so you can get out if it sounds like people are having bad experiences with them.
This is a largely unregulated area. So you have to do a lot more homework. There's no "Well I'm sure they wouldn't let them operate if they weren't on the level," or "I'm sure they wouldn't let them advertise if they were crooks." Sportsbooks range from legitimate companies roughly as safe as "conventional" big name businesses, to the equivalent of Nigerian e-mail scams, and everything in between.
6. Shop lines and shop odds.
The more accounts you have, the more you can shop. Don't make a bet at -4.5 when -4 is available. Don't make a bet at -120 when -115 is available. (-120 means the odds are such that you have to risk $120 to win $100; -115 means the odds are such that you have to risk $115 to win $100.) Often the difference is slight, but those pennies add up.
7. Learn how to scalp and middle.
If you have multiple accounts funded, you can sometimes come upon opportunities to play both sides of a bet at different places. So maybe you can get -3 on one team at one sportsbook and +4 on their opponent at another. (That's a "middle.") Or maybe you can get +180 on one team at one sportsbook and -175 on their opponent at another. (That's a "scalp.")
In effect, scalps and middles reverse the house edge to put you in the position of advantage.
8. Take bonuses.
Most online sportsbooks offer incentives and perks of various kinds to get business. The most common is a sign-up bonus on your initial deposit. A 20% sign-up bonus, for instance, means if you send them $1,000, instead of depositing $1,000 in your account, they'll deposit $1,200.
You can also sometimes get bonuses for subsequent deposits if you happen to lose your whole balance, referral bonuses for other customers who sign up that you recommended, and more.
Don't get too caught up in the "free money" and lose sight of whether these are places you'd want to play for other reasons (safety, good betting opportunities), but bonuses can be a nice boost to one's bottom line.
Some bonuses are of more complicated types, such as a "free play" instead of cash. Be sure to research how to use any such bonus, because there can be big differences in its value (that wouldn't be obvious to a beginner) depending on how you use it.
9. Don't buy "picks."
Total waste of money. Total scam. Success as a tout is all about marketing, not handicapping. Don't get caught up in that.
If you absolutely have to follow someone else's picks rather than do your own work, there are no shortage of handicappers on the sportsbetting forums who share their picks with each other and the public for free just because they enjoy this activity or it boosts their ego for people to see them pick winners. On average they're as good or better than the people trying to sell you their picks.
10. Research, crunch numbers.
For example, learn more than the betting public about how much a team's roster was helped by free agency or the draft, or how likely it is their injured starters will be able to play in their next game.
Learn whether it's better to take +7 at -110 odds, or +6.5 at even money. (Depends on how often games land right on 7. Find out.)
I knew a bettor who made a fortune betting "in game" or "in progress" wagers. (These are bets a few shops offer where you can continue betting throughout a game as the odds change.) How? He spent thousands of hours compiling meticulously detailed charts to match every game situation.
For example, let's say an NBA team is playing at home and is favored by 5. There are currently 7 minutes left in the 3rd quarter and they are up by 2. They are about to in bound the ball from center court. He could tell you in the history of the NBA, what percentage of the time a team falling under that description in precisely those circumstances went on to win by more than 5. (Which he could then adjust for unique circumstances like if a key player was injured during the game or was in foul trouble.)
How well do you think he did against the average bettor operating at the level of "I really like the Knicks here. They have the momentum; I think they're going to pull away"? Which would you rather be?
11. Look for obscure angles other people don't know about.
Years ago I remember a bettor who made a lot of money on golf telling me that a certain golf tournament has a tradition of making the pin placements particularly difficult on Day 4. So he'd look for shops offering props on individual golfer scores on that day, and bet the Over (remember, in golf low scores are better than high scores) on all of them.
When NASCAR first became a big sport, neither the betting public nor the oddsmakers were all that knowledgeable about the ins and outs of the sport. For awhile, they grossly underestimated the importance of the qualifying rounds. Drivers that qualified with the highest speeds barely had their odds adjusted for the race itself, whereas in reality their likelihood of doing well increased a lot more than that. So savvy bettors who knew that cashed in.
You want a really obscure one? I knew a bettor who found out awhile back that every season Shaquille O'Neal would dedicate a game to his grandmother on her birthday, and he would almost always put up big numbers that day. So each season, whatever game was played on or closest to that date, this guy would go to sportsbooks that put up basketball props, and he'd bet the Over on O'Neal points and rebounds and such, and he'd make a nice chunk of change.
How the heck would a person know about something like these? Well, when you treat this as your job, and you spend hours every day reading newspapers, reading websites, talking to other successful gamblers, etc., you find little nuggets.
12. Learn about all the non-conventional bet types.
There are times parlays are more advantageous than straight bets. Same with teasers. There are times it might make more sense to bet a half or a quarter than a whole game. Occasionally (rarely) it's to your advantageous to move the line by "buying points." And so on.
Find out what those occasions are and why.
If you limit yourself to making straight bets on whole games like 90% of gamblers, you'll miss all this.
13. Disregard all betting "systems" that purport to give you an edge by how you alter bet size.
You simply cannot overcome (or even change) a house edge against you by how you order your bets. (This is true of casino games like craps or roulette as well.) Any system of "double up after a loss, then start over at a win," or "bet one unit until you win at least three in a row, then bet 2 units until you lose two in a row, then bet one unit," or whatever is mathematical garbage. Period.
OK, we'll stop at a lucky 13.
Good luck with your wagering. But better yet, bet smart and let the luck take care of itself over the long run.