Usage patterns
〈人〉に技をかけるto apply/execute a technique on someone (esp. in martial arts)
The athlete executed a brilliant technique on his opponent.
技が決まるfor a technique to land successfully
The impressive technique landed perfectly, and the crowd went wild.
技を身につけるto master/acquire a technique
After years of practice, I mastered this technique.
技を競うto compete in skill/technique
At the competition, each athlete showed off their techniques against one another.
Expressions
技を磨くimprove one's skill; polish one's technique