1 Draw them in the summer when the water is warmer
2 Find the hot spot, best are the tributaries, then where the current of the river forms the "reversals" (like the picture below), if you have a boat you can get out with the current and cast the bait a few cm from the vegetation of the banks, if you don't like want to work hard you can sit in a point of strong current launch a minnow shallow in the river and let the current work for you.
3 Fish them when the river is rising after rain or better at the height of the full (I do not have experience in this regard, however, it seems that with the river at normal levels you can make good catch at night)
4 look at the River, see catfish hunt afloat, well large minnow type super shad rap or tadpolly or salmo perch in larger sizes are excellent bait, but if the cat ignore them you can also use smaller fish also shad rap 7 cm that make little noise. If you see nothing on top water it may be a good idea to get off the bottom, excellent baits are downunder (with the biggest lip I ever seen), the rare downdeep fat rap, or the little but deadly dives-to (I think it's on + - 7cm)
5 Change the treble hooks and replace them with strongest, if you lose for this reason the only fish of the day is not nice
6 Ok, now let only a pair of strong gloves to bring the fish on shore
Talking about asp here the best time for rapfen is in october, november when you can catch the big one, my favorites lure are propeller, walking the dog, slider jerkbaits and minnows but go equally well spoon, in line spinner, crankbaits, lipless and lipless crank, grubs on jighead reeled very very fast
when they bite the lure give tremendous barrel 
however it like the stuff that shines and turns, my spots are the prismatic Riverside waterfalls and the areas between two different currents of the River, on evening in summer in stagnant water (oxbows) I have caught some bigs on topwater!! 
