A lot of people have given good advice on this thread; I'd just add four things:

1. Make sure you have really good next actions. I usually find that my worst procrastination comes when I have a task that look like a next action but is actually too big to be a single action. David Allen talks about this a lot in GTD and it's worth reviewing, I think.

2. Give yourself permission to not be perfect. I'm a perfectionist, and so I put off a lot of tasks because I can't do them perfectly. My solution is to make an agreement with myself as to specifically what outcome I expect when I put a task on my to-do list. When you think through what you actually need, it's clear where perfection is valuable and where it's not worth it.

3. Make a list of what you're putting off. I did this and found out that I was always putting off sales calls -- because I just wasn't good at them. So, I talked to some salespeople I know about how to be a better salesperson, bought a sales book I heard recommended, and took an improv class. I'm now a lot more comfortable with sales calls, and am more successful at them too. It's reasonable to put off things that simply can't be done well, and sometimes this points us to what we need to learn to do better.

4. Reassess your responsibilities. When you look at the list from #3, what's on it? Should you really be doing these things? If some are not appropriate to you, can you talk to your boss about them and trade them for other responsibilities? Can some things just not get done? A recent example for me comes from my personal life -- my girlfriend, who's got a green thumb, gave me some really beautiful plants that required a lot of upkeep. I just wasn't taking care of them, and they were looking quite sad for it. I reassessed my priorities and realized that I just didn't care about plants nearly as much as she did, so I gave back the plants and she replaced the gifts with some hardier specimens that I can take proper care of and get happiness from. Everyone ended up happier from that.

I'm an awful procrastinator -- a perfectionist, and lazy to boot. But I get a lot done by watching myself with these techniques all the time.