I play a few characters, Marth, Samus, Falco, Falcon
If you posess the knowledge, generally it's just a matter of warming up which takes more or less time depending upon the person.
what I usually do is start with the character that takes the least tech, which is generally Marth or Samus, then after playing for a bit with them - I usually play a level 9 bowser or a level 1 anyone (usually for figuring out combos on other characters)..this doesn't help with tech chases or dealing with DI, but it will et you into the habit of starting to follow up hits with things that could combo.
Usually after playing Samus or Marth or whoever else takes little tech, then I can switch when I see my self landing most of the wavelands and l-cancels and stuff (warmed up), then I can move on to more tech heavy characters, like Falco and Falcon...then I can do 0 to death combos on the comp almost per stock.
Also, if you need general tech help, just go on practice and run around on the stage for like a few hours (seriously it helps, I used to do this daily for hours), once you can move around good, start throwing in lasers, kicks, l-canceling just whatever..keep running around while doing attacks and such. It might be boring but it helps tons. This is my practice method, anyway...I almost never play anyone irl.
OH! I can't stress how awesome learning to properly ledge drop is too, just saying. LEARN IT if you haven't already
