Some of this will depend on the style you practice. Also, you should really be asking your instructor or senior student who can see what you are doing and make specific suggestions. Having said that, focus is important, but don't focus on "speed". Focus on the technique, and focus on relaxing. Many people try to get faster, but they end up tensing the wrong muscles, and actually slow themselves down.
One practice that we have done is to throw techniques with a "soft hand" (in the air, not against a target). This tends to soften the rest of your arm as well, helping to relax everything that isn't required for the proper technique. After you get a sense sense of this kind of movement, then you can return to your more rigid striking point (i.e. making a fist). This will also make you focus on proper power production -- through the body, instead of the with arm (which might also be slowing you down).
If you're talking about speed through an entire form, we also had another saying "practice slow to get fast", which is essentially what the other poster was mentioning -- drill proper mechanics until they are in the muscle memory, then let them flow into greater speed.
If you're talking about hand speed in general, you could try training with a speed bad or target pads with a partner. Still, with these you have to learn to relax and let the techniques flow to achieve any real, lasting speed.
But really, talk to your instructor. They can see what you're doing and give you tips that will be most appropriate for your specific problems and your specific style.