It very much depends on a few things:
- Your level of experience
- The length and quality of your nightly sleep
- How often you are able to practice techniques
If you're a beginner and you get at least 7 hours of sleep a night, I suggest MILD. Wake up after 6 hours of sleep (not 6 hours in bed, there's a difference - you want to hit that REM period, so if it takes 30 minutes to fall asleep, add 35-40 minutes to your alarm just to be safe) and repeat your chosen mantra (my mantra of choice since 2010/11 has been "I will be lucid in my next dream" but choose one that feels right to you) for 1-2 minutes, then go back to sleep. It also helps to imagine and visualise your dream beforehand but sometimes you'll be too tired so just repeating the mantra briefly is enough.
If you're a beginner who gets less sleep than that, I suggest finding the next closest REM period (i.e. ~4 hours 30 if you can't do 6, 3 hours if you can't do 4.30, and 90 minutes if you can't do 3 hours) or chaining naps by taking a 2 hour period in the middle of the day and setting alarms to wake you every 10 minutes. (keep going through the alarms until you wake up from a dream - that means you're in REM) then perform the mantra and go back to sleep.
Once you've had your first lucid dream and know what it is like, then it really depends how much time you want to dedicate to lucid dreaming. If you're not able to practice often, or are limited on time, I suggest just using MILD whenever you're able (you can also use it during the night if you wake up in the middle of a dream).
If you're willing to dedicate some time each day to lucid dreaming, I suggest starting a dream journal if you haven't already, and also performing regular reality checks - the hit rate for these is typically smaller than other methods like MILD etc but the point is that when you do hit and succeed in getting lucid, you're doing it during the other dreams that would normally have been non-lucid dreams. So you can combine this with MILD to get way more lucid dreams than you would have with MILD alone.
If you have some extra time and patience on top of that, then that's when I suggest learning the likes of WILD, FILD, and other direct techniques. With these techniques, if you hit an REM period, and do everything right, it's almost a 100% success rate. The trouble with these methods is more the time it takes to learn them, since it's often very hard to describe how to do these in a way that the other person is then able to replicate 100%. I hear about it all the time, people thinking you need to enter sleep paralysis for WILD (completely wrong!), people violently wiggling their fingers like their hand is having a seizure for FILD, etc.
Once you have some experience under your belt, then I find that the best technique for me personally these days is none of the above, it's simply: Meditation. I discovered it by accident. I've been meditating daily since early 2015, and a few months ago I started being more consistent in the length of my meditation, and moving it to before bed. When I started doing this, I noticed that all my dreams were lucid all of a sudden, and within a week I had a night where I had 11 lucid dreams in one night - then a couple of weeks later, 13 in one night! It was pretty crazy. I wasn't performing any techniques whatsoever during this time, just meditating for 20-30+ minutes every night around 1-2 hours before going to bed.
Personally I think everyone should be meditating daily - beginner or advanced, since meditation has so many important benefits outside of lucid dreaming.. but that said, for purely lucid dreaming benefits, I've noticed that beginners seem to get less from it - while more experienced lucid dreamers seem to find it gives them a crazy amount of LDs.
So in summary:
- WILD and nightly meditation have the highest % success rate for me, but require some experience
- MILD is the hardest technique to mess up (about the only thing you can do wrong is set your alarm in such a way that you don't wake up in REM) and so the best choice for a beginner
- RCs etc are a good addition to the above