First of all, you should be aware that at professional levels, the (jump) smash is the shot to end a rally (or to prepare a kill shot). Especially in doubles, but also high-level (Men's) singles, players fight for the chance to smash downwards, i.e. try to avoid lifting as much as possible. Sometimes, the easiest way to defend against smashes is not lifting in the first place, and rather playing flat or short. This may necessitate taking shots earlier at the net then you currently are.
Another aspect to watch is the distance and angle of your lift. Analyze (e.g. via video or having a friend record) where the smash started. Smashes from the midcourt or even forecort are nearly impossible to defend against. In Men's singles/doubles, if your lift did not reach the doubles service line, then it is far too short. Additionally, look at the angle of the lift: A flat shot is both easier to hit and already has more energy. If possible, your lift should come down vertically.
The defensive technique begins with the proper footwork. On your forehand side, one step should be enough for sufficiently tall players. On your backhand side, you have two options: Either a small step with your non-racket-arm foot, or stepping over (i.e. body moved away from the net) with your racket-arm foot. For smashes toward the very line, you need the latter unless you are extremely tall.
You have three basic options for your shot: Short, flat, and high. Unless the shot is going far to your racket-arm side, defensive shots are easier with the backhand.
In singles it is usually a good idea to play a short shot, in order to gain the attack yourself, so that you can be the one smashing. However, beware of your opponent storming to the net in order to kill your defense. It is not a trick per se, but you should be able to hit longline as well as cross-court shots. The latter force your opponent to cover a great distance, and are thus usually best if you can consistently hit them.
In doubles, a short defense must be quite good in order to evade the partner of the smasher. Oftentimes, it is better to counter with a flat and fast defense that goes around the front player. If your defense is angled really flat, there's a good chance that you'll end up in a neutral or even attacking situation.
To train your defense, there are multiple options, depending on your level of play (and the level of skills of your coach):
- Make sure your footwork technique is correct by doing the footwork for far-right / far-left defenses without a shuttle. Have a coach watch you and note details, such as unnecessary small steps or suboptimal racket preparation.
- To get a feel for the shot, you can hit shuttles thrown to you from about 3 meters distance. The feeder should wear safety goggles, especially when you're training fast and flat defenses. You can start by defending shuttles thrown to your body and advance to shuttles thrown at the side lines.
- Better, but harder than throwing, is hitting shuttles, typically from the net. The coach just pushes the shuttles downwards (like this). If your coach lacks the necessary skill to hit the shots downwards in this fashion, a machine can also be used. Again, you can start by defending shots to your body or the general vicinity, and graduate to shots going to the sidelines, as well as shorter/longer and with higher frequency.
- Finally you simply defend shots in an exercise: You lift everything (or defend short to the net, after which your next shot will be a lift) and your partner smashes everything downwards. It is harder to control for frequency and accuracy, but it's the only way you'll learn to read your opponent's technique in order to anticipate where and how to defend.