Start digging! I dug it all with a 6 foot iron digging pole (weighs about 25 pounds but breaks things up real well). Make sure you know where your pipes are.
Include many different depths -- energy exists along boundaries -- so everything that wants to live in it can.
Have at least one side on which small animals can get a drink (shallow beach vs sheer rock.
Go a bit deeper than you want the bottom to be since you'll have some sort of rocks in the bottom over your liner. I splurged on a HDPE liner.
If you have rocks on your property, use those in the pond.
If you want fries and salamander, don't add fish.
Leave overhangs underwater to give things a place to hide.
If you know someone with a healthy pond, get a bucket of their water and done plant cuttings to get a jump start on biodiversity.
I'll think of some more later!
Hahaha fries* was supposed to be frogs!