Are you referring to when you have the ball? Or when you don't
have the ball? Or both?
Without the ball:
1. Use Screens
: As empire said, even using unintentional screens (running near a teammate) can help create just enough separation needed to put oneself in position to receive a pass and square up.
2. Stay On Your Toes, Keep Moving
: If you're really struggling to create separation, make sure you're not flat footed and making easy cuts. When I say "keep moving", I don't literally mean running at every given second, but try not to stay in the same place for longer than a couple of seconds. Make your movements sharp.
3. Use Baseline As A Runway
: Attempt to speed from one side of the baseline to the other, using a screen if it's available. The defender should be looking to beat you to a spot. If they're playing super tight, this could very well allow you to set your feet, reverse path, and come back out the same side with a little separation.
4. Get Your Feet Wet
: Maybe I should have mentioned this one before the baseline thing. Getting your feet wet was a term we used to refer to putting both feet down into the paint before V-cutting.
Usually, even when guarded tightly, you should be able to lead your man down into the paint, even if it takes a little contact and grappling. Once you've led this player to the paint, he should be between you and the basket. From there, using your body and some savvy and simple footwork, you should be able to initiate contact, give yourself a head start and pop out and open via V- or L-cut (L-cut being a lead up to the elbow, then some contact with the defender before making a 90 degree angle cut out to the wing).
5. Post Up
: If a defender is comparable in size and is unwilling to give up a simple cut (or a complex cut), I say attempt to seal him by putting your back to the basket, making yourself large, and creating a passing target for your teammate. If you're able to successfully secure possession in this manner, regardless of where you are on the floor (even if you're 18 feet away), if you catch the ball with your back to the basket you should still be able to face and square up with a pivot.
All that said, if the problem is getting separation with
the ball then:
1. Do Not Waste Your Dribble
: When someone is playing extremely tight defense on me and it's a problem while I have a live dribble, I'll often look to give the rock up and get it back... just so I can operate from triple threat.
A lot of players have a habit of receiving a pass and initiating a dribble without having any real purpose or reason. They've got nowhere they need to go and no moves they plan on making right away, they're just dribbling to dribble. Against a great defender, this can be hazardous, as initiating a live dribble removes half the possible maneuvers in one's repertoire.
If you're able to secure the ball without having used your dribble, you're going to be in good shape. A really, really tight defender will often have a couple of big weaknesses. Primarily, guarding so tightly means he must respond to any quick or sudden movements on his opponent's end. This is why I highly recommend being well-versed in triple threat maneuvers. This would include: stepping through (physically creating space by pivoting toward the defender) and jabbing (feigning quickly in one direction with the foot that isn't planted).
Running theme on close defenders: If you're able to get them to shift their body weight just ever so slightly in one direction, it's likely to open a big opportunity for you offensively. Guarding so close does not leave those guys a safety net. If they make a small mistake, they're often done.
2. Keep It Simple
: It's easy to get caught in the mindset that players like Allen Iverson lose their defenders through a series of incredible dribbling moves but the truth for most players in the world is that it's easier than that. You don't usually need a double cross to behind the back dribble fake to elude a tight defender. Sometimes a quick in-and-out will be enough to create space or evoke a response. In fact, sometimes even running in one direction then hesitating for a moment can be enough as again, a defender guarding that closely must respond to everything more suddenly than if he were providing a little bit of space.
In summary, I guess I'd recommend
-Initiating Body Contact
-Getting One's Feet Wet
-V-cutting, L-cutting, Cutting
-Fakes, Fakes, Fakes (ball fakes, jab steps, shot fakes, step fakes)
-Confidence (know they're at a disadvantage)
Also, I like this video via Richard Hamilton: http://www.youtube.com/watch?v=PzLA78Qb3fg