I do not target recently stocked fish, indeed I avoid them once found. Introduced fish take time to settle down and become educated. The catching of 'stockies' requires little skill and consequently returns little satisfaction. Targeting these fish makes the whole stillwater scene artificial. It can be hard enough sometimes to justify the fishing of stocked waters.
However, the only way to become fully contemptuous of 'stockies' is to catch them. For beginners I can see the value in getting fish 'under your belt'. They are pretty tasteless - tasting of pellets, and fight poorly - due to their condition. But here's how to get them:
Stockfish often are induced by bright attractors, with plenty of movement incorporated in the dressing.
Hare's ears' and pheasant tails nymphs resemble pellets.
Flies moved at quick speeds often causes interest, also try jerky retrieves.
When you find one stocky, more are likely to follow - get your flies back in the water as quickly as possible since they shoal very tightly.
After stocking the fish tend to move upwind, you can track them.
Splashing attracts stock fish. In cages when netting a few fish (I used to work on a fishery) holding one fish has near the surface has the result that many others swim close by (they think the fish has found food), this means that if you are catching fish, you are likely to encourage others into the neighbourhood and also that you have an increased chance of catching fish more than one at a time.