Great advice here on technique / strength / weight loss / etc. I have surfed since I was little but due to poor technique, poor mobility, long legs & tight hips/ankles, I still botch way too many takeoffs, especially in crap waves. (steeper waves allow my board to drop down the face and seem to give me more space for my legs/feet to simply slide into position)
Here is what has been helping me a ton this past year:
1) Ido Portal's 30 day squat challenge. (30 minutes of squatting per day, for 30 days)
2) Dialing in technique (wave ki breakdown is pretty helpful actually - "sliding" to your feet vs. "popping up")
3) Along with #1 - directly targeting improving hip and ankle mobility, by doing the following before each surf session:
a) simple warmup of ~20 air squats and then these 2 stretches:
b) Cossack Squat holding on to a fixed object in front, so I can lean into the bent leg and get max stretch of achilles + soleus (secondary inner thigh stretch on other leg). 2 minutes each side.
c) Figure 4 stretch on floor, to stretch outer hip / it band / upper hamstring (for better squat mobility) - 2 min each side (it's kind of like this stretch, but with back leg also bent instead of straight back, and back folding to stretch front leg:
https://hips.hearstapps.com/hmg-prod.s3.amazonaws.com/images/0904-figure-4-stretch-1441032989.jpg)
Results: I used to not be able to hold a low "asian" squat at all (I would just fall back because my hips and ankles were too tight), but now after a little bit of warm up I can hang out in the squat pretty comfortably with no support our counterweight, even with bare feet. Prone-to-feet consistency (and surfing performance) has definitely improved also.