I remove the distractions. Quit email, IM, IRC, work from home in a quiet place. Few people have my phone number, and they know not to call me unless their hair

I remove the distractions. Quit email, IM, IRC, work from home in a quiet place. Few people have my phone number, and they know not to call me unless their hair is on fire. The right kind of music can help too. If I'm struggling to focus, I do some exercising, go for a walk (sunlight helps) or just take a break away from the work and come back refreshed. If I'm still struggling, I just give up and start again the next day (where possible - deadlines are a good motivator too, but not if overused). If I can't focus because I'm tired, I take a nap. I reserve caffeine for emergencies ("must get this done today") and with a two week cooldown afterwards (you'd be shocked what caffeine can do for you in a pinch if you haven't built up a tolerance from constantly abusing it). Most importantly, look at what you're doing. I have little trouble focusing on something I want to do. It's the tedious bits that I struggle with, and so if I find something like that, I try to eliminate it as much as possible. This means picking your projects/clients/job carefully, and not rating money as top priority.