This all depends on how long you have been training for. Basically, advanced techniques like forced reps or drop sets can be used about 3 months after you have started training because that is when you typically hit a plateau. So if you feel like you need something changed, if strength or muscle gains have come to a halt, then advanced techniques may be good for you to try. Forced reps, where you have a training partner help you through a few additional reps after hitting initial failure, are a good place to start as long as you do not overdo them.
Forced reps with a partner is a good technique to use for new growth, as it gives the muscle more stimulus after the mind and the muscle is disconnect and you are physically unable to complete any more reps without help. Using the bench press as an example, load the bar with a slightly heavier weight than you might use when training alone. Aim for got your target number of reps on your own, even if you know you may fall short by one or two reps. If you are going for 10 reps for example, and fail at 8, you can use forced reps to complete the set. Have your partner hold the bar lightly on the descent, then help your power it back up to the top, offering only as much help as necessary for you to complete the rep. This is where a good training partner comes in handy. You want someone who is familiar with your limits and who can safely help through the set.