Just joined Fluther yesterday so the advice is a bit late, but in general:
Take every opportunity to watch your opponents fence in other bouts before you meet them on the strip.
Take notes after every pool bout on how each particular opponent scored touches against you and how you scored touches against them. Use what you learned in the pools to your advantage in the DEs and keep this information over time because chances are you will be seeing them again at another tournament and you can rest assured that they have been watching you as well and the next time you meet them it is likely that they have been working on the exact skill they need to beat you.
Physical conditioning is important, but never forget that fencing is as tactical as it is athletic. Learn the tactical wheel and use it!
What weapon?
What part of the country are you in? My son, along with several others from our club, will be fencing in the RYC in Houston this weekend. Perhaps I’ll see you there.