How to make money sports investing;
I've been gambling for a decade, profitably for 2-3 years.  I became a student of the practice.  Reading books, blogs, articles, questioning the greats on forums, blogs, websites, and simply trying countless systems. There is a ton of information out there, but bottom line, anyone can be profitable if they follow a few simple rules;

1) Money management
This is the single most important thing and the reason 80% of gamblers fail. For the sake of space and time, for today I will briefly mention a few components of money management (MM), without going into too much detail.  
  Units - Each bet should be a unit (a percentage of your bankroll between 1-5%).  Some people run different systems with different unit amounts, but for a beginner, and most experts each play should simply be 1 unit at around 3%.
  Goals - The power of intention is strong.  Set yourself goals so you aren't playing just to play.  Whether that be weekly, monthly or monetary goals, reach them and reset them.
 Discipline - Another rookie mistake;  losing two games in a row so playing 3 times as much on the third.  To be profitable you need to stop this (ties into rule #3). How many of us were up 10 units, only to pop into sportsbook casino's and lose it all?  Dont' chase (unless it's part of your style), stay out of the casino's, and stick with your unit system.  Always. Or YOU WILL LOSE IN THE LONG RUN. 
 Keep a record - Over looked by some of the greats as well, keeping a record is key.  How else do you realize that you are 60% on sides but 35% on totals?  This is how you discover that you are great at the start of seasons, but historically bad at the end, or after all star breaks, holidays, etc.  This also keeps your accounting honest, and helps with discipline.
 Lose the risky bets - Probably  the most controversial thing I will say, for some of you.  Parlays, teasers, "if bets", etc are all money losers.  Sure there are a few on these sites who do OK with them, but for the most part, they really are bad value bet.  If they are part of your style, then at the least try to keep them to a minimum, and keep them between 2-3 games.  

2) Choose your style and sticking with it
Cannot be understated as this is how you actually choose your picks.  Finding a style that works for you and sticking with it, even through the inevitable downturns, is rule #2.   Once again, I will just touch on some of the styles.  Feel free to let me know about your own style, and at some point in the future (if anyone reads this) I will break each style down further.  Yes, I've tried or tracked all of these for at least a few weeks in different sports.
Line movement, trends, gut feeling, motivation, public plays vs fading, refs, following specific cappers, weather, injuries, rest&travel, "magic numbers", labouchere system,  martingale system, etc.  
To be profitable, you obviously have to pick winners.  However, this is still not as important as MM.   I have seen a ton of people over the years hit 60% and still lose their bankroll.  

3) Lose the emotion
Another bankroll killer, rule #3 ties into money management.  To be profitable, we need to lose as much emotion surrounding our plays as possible. It is when you are pissed that the red sox missed the cover in the 9th, on an error, that you are more likely to chase your losses the next game. Alternatively, when they are your third win of the day, we have a tendency to feel lucky and blow all of our profits on game 4. 
Don't bet on your home team if you can help it, it's not worth the grey hair.  Some people will go so far as to say do not watch the games you bet on, but I think that depends on your style.   
Last, but definitely not least, DO NOT PLAY JUST FOR ACTION.  We get so used to the rush of betting that we often make bets just to have "action".  Don't do that. 

This is the very basics of sports wagering, from my perspective, after a fairly exhaustive search.  I am confident that anyone who can follow these rules will be at worst, a break even better.  With the proper style, strict money management, and losing the emotion associated with your bets, anyone can take the leap from being a sports gambler to becoming a sports investor.