I’m relatively new to winter fishing, but from what I have gathered deeper (5-8’) holes out of current but with current nearby, and rock structure.  Are there any other key giveaways? Thx!

Winter can be high water times too. if your river is 4-5ft above normal flow check creek mouths. Any kind of water release from a dam or power station can still hold fish as well. They may not been in a foot or two of water but, don’t over think that they went too far either. 

Usually rocky bottom with a big enough current break to shield them even in high water flows.  Depth is relative the river system.  Small flows a winter hole may be 4' deep, and in bigger flows you may need to find 10'+.  A recent trip yielded some nice ones that were holding behind big isolated boulders in slow current, water was 46.

Small rivers suck in winter, big ones with dams are much better 

 

everywhere I’ve caught winter smallies, it’s 10+ feet deep one step off the bank 

I should add, the small shallow rivers can be good after a warm rain when they get up into the 50s really fast. They will warm faster that deep waters, so they do have a place for some parts of winter. But I would much much much much rather fish a deeper river/lake with water temperature stability in winter , the fish seem to be more consistently hungry 

Ive had 50 fish days in knee deep water that was about 39 degrees. River fish dont need to expend near the energy in fast water, they pitch and yaw like airplanes.