Unless the pad or tone hole has a serious problem, common or garden sticking pad syndrome can be cured by application of lighter fluid. Do not use talcum powder, WD 40, or any proprietary remedy, many of which are rip-offs and will only cure the symptoms temporarily, while making the problem worse in the long run.
Sometimes it is necessary to strengthen the spring. You can make your own tool for this: break the lead off a pencil and use it to hook the spring out and retention it, but if in doubt get a qualified repairer for this.