i always write down the values that i'm already given; then i write down a question mark next the value i'm trying to find. Then i just try and think of the equation that uses the values i have/need.
But yeah, sometimes the question gives you enough information to use more than one suvat; in which case i just pick any
Write down "SUVAT" then next to the thing you need to find, put a question mark. Fill in other things given to you in the question (remember, if it tells you something starts from rest then u=0 and if it is falling down then a=-9.81) cross out the remaining letter. Use the equation that has all four letters shown.