Signals are often the difference between beating a contract and not; used correctly, they're invaluable. There are a few important decisions to make with them:
Which signals will your partnership use?
When do they apply? A big source of confusion is the two players being on a different page about which signal is being given — one might be giving count while the other reads it as attitude about a suit. Having crystal-clear, consistent rules around this is essential.
Keep it simple; don't overdo it. One or two simple but reliable signals will often achieve the goal.
Modern partnerships are building a lot of suit preference into their signalling — the play of irrelevant pips can be made to carry rich information. But, as always, keep it simple and don't overdo it, especially at the intermediate stage: one or two signals per hand will be sufficient.