I will begin this by saying that I have no qualms with boosting and I think the 2 guides already posted are excellent for those attempting to boost. Me personally, I got frustrated trying to boost this game as I could never get matched with anyone. I went for this and the streak achievements normal, and this guide contains tips for anyone else going for this without boosting:
First, most people online use the "power" teams. By that I mean you will almost always play against the Heat or the Lakers and occasionally the Celtics. A great team against all of these is the Thunder. I got all my wins using them and I was blowing people out without having to adjust the settings too much.
Tips while using the Thunder:
-Don't jack up shots with Durant nor try to drive all game with Durant. My opponents would usually forget about him by halftime and I could find him alone on the perimeter for a wide open shot. This is his strength.
-Use the 1-3-1 defense! This stops so many people online it almost isn't fair. People using the Heat/Lakers try to drive against you all game, and this defense stops them. Plus, when you get the rebound or steal (and you will get a lot of steals with this on interior passes), you have Westbrook and Hardin out on the break for easy lay-ups.
-Speaking of which, swap out Hardin for Sefalosha in the starting line-up. I turned subs on manual/fatigue and never had problems. Yes, Sefalosha is a better perimeter shooter, but you shouldn't be depending on 3's to win.
-Get Westbrook hot early with some of those fast-break lay-ups and he is unstoppable driving the lane later in half-court sets.
-Most offense possesions went like this for me: back down the defender with Westbrook near the top of the key (hold both triggers to do this). The CPU does a good job of automatically cutting to the basket when you do this. Your opponent is most likely playing on-ball, so it becomes sinfully easy to just toss a pass to a wide open man for a lay-up.
-I very rarely played on-ball defense, instead playing one of the wing players to deny passing lanes. People online abuse isomotion and they will get by you if you're controlling the defender. Plus, they would normally be expecting me to be controlling on-ball, so it would throw them off when they couldn't just dribble past the CPU defender!
-Last tip and probably the most important: play with the 2K camera from Myplayer! It takes a bit of getting used to, but once you are used to it you'll be unstoppable. I think it is much easier to play defense in this angle as you can see those passing lanes clearly.
That is pretty much it, just expect to put some time in if you're going for this legit. By using these tips, I quickly got to where I was blowing out almost every opponent by 15 or more and was getting alleys on many plays. I'm not crazy good at the game either, and struggled for like 20 games using the power teams before I switched to the Thunder, then got like 15 wins in a day or 2. Have fun!