I'm new to all this too and have sand ... my fish haven't created much debris yet but while I was cycling I had a TON of debris from the fabulous seeded filter media I was given to jump start my cycle. I kept shaking it in the tank, based on a recommendation to do so in order to get the bacteria to populate all the surfaces.
Anyway. I had a lot of chances to practice and there's this sweet spot with the siphon, where it's close enough to get the crud but not to get the sand. Waving it around a little does get the poo to float without stirring up the sand too much.
Definitely going to try the raking method!
Also, I found a way to do frequent small water changes with practically no attention, in a way that doesn't mess with the sand:
I got a 25' piece of silicone aquarium tubing and a few of the suction cups that hold it. I put one end about midway into the aquarium, and the other end in the bath tub (or my garden, or whatever is lower than the aquarium). It's easier than I expected to start it siphoning and the siphon keeps itself going better than with a gravel vac. Then I walk away, do a little laundry ... next thing I know it's emptied about 15% of the water from my 29 gallon. It can't over-empty without my noticing because it's so slow and I've pinned the end of the tubing where I want it. I do shut off the power head and keep the tubing above the filter intake so the filter keeps going.
Then I fill my bucket with good conditioned water, stick the "bathtub" end of the tube in the bucket with another suction cup to keep it in place, put the bucket higher than the aquarium (in this case, on my bathroom counter) ... the siphon automatically reverses with the gravity.
Anyway, it's been a pretty cool way to get in several little water changes a week, in a way that doesn't disturb the sand and gives the fish an extremely gradual adjustment if the new water is a little different than the tank.
Finally ... since I chose to put in a power head for current, I sometimes place it where it will stir up the lightweight stuff on the bottom without messing with the sand too much. Then the filter gets more of it, and what the filter doesn't get ends up in one front corner.
I asked the same thing before I got sand.
