First of all, if you're seasoning tilapia, you'll want to add some oil to it, since tilapia has almost no fat. So, here's the steps:
- Drizzle oil over the tilapia (both sides).
- Sprinkle it lightly with the spice mixture, all over
- Let sit 10-15 minutes.
- Sprinkle with starch (e.g. flour) at this point if you're frying them.
Optionally, you can also add some lemon or lime juice (just a little) in step 1. You also want the tilapia sitting on something flat, with the filets in one layer, like a large plate or baking sheet, not heaped up in a bowl.
For spicing small filets, you want a finely ground, moderate-flavor spice mixture. Unlike beef or pork, you're not marinating the fish for a long time, and you're not cooking it for along time. So the spicing on the fish isn't really a "rub"; it's spicing to eat. I recommend against using rubs designed for meat on light fish like tilapia.