1. Docks are good year round but they really excel during the Summer when the sun gets high.
2. I like a jig, shaky head, senko, or frog.
3. Docks that are set in the ground (non fluctuating docks) seem to be the best. Any rocks or brush underneath a dock is always a plus.
4. Deep docks are good during the Summer and Winter, shallow docks are good during the Fall and Spring. If your lake gets a lot of pressure, look for the ugliest, shallowest docks on the lake because anglers often overlook them.
Solid Gold right there!
To add to it, let the fish tell you what to do, don't go in fishing docks assuming anything. General rule is early morning they'll be on the edges of the dock or even in open water next to the docks. Top waters, small squarebills and various other baits will catch. Cloud cover extends this bite. As the sun gets up, the fish will generally move back to the shade. Let water clarity tell you how deep, clearer the water, deeper the fish. Dirtier the water, the more shallow they'll be. Most lakes in Texas you can catch them in 2-5' of water in the docks in summer and winter.
Get good with a spinning rod. Once you can skip your bait so far back you only hear it stop (and can't see it), you're there. Getting a bait to fish that other people can't is key, especially on pressured lakes. Don't believe the hype that a "fairy wand" won't catch big fish in boathouses. I have many over 7 and one pushing 10 from deep under boathouses and some were stuck in brush piles. 30 lb braid and 20 lb fluoro leader and I've yet to get beat by a fish. Even have a 30 lb Op that was in some kind of metal, I could hear my shaky head clanging steel when the fish hit.
On clear lake deep docks, skip something weightless and let it fall vertically, or swim a swim jig out at varying depths. Most of the time those fish suspend, I'm talking about clear lakes with floating boathouses in 20+ foot of water.
Wind on the docks can make all the difference in the world, but will make skipping a challenge.
Not all docks are the same, and not all fish in each lake act the same. You may have to fish a stretch of 20 docks only to find a group of 3 that have fish. Pay attention to why. Are they on the end of a point, are they shallower, do they have vegetation close by, do they have rip rap on the bank, is there a retaining wall. Work every dock thoroughly. I have seen many times where you could work the front of a dock and skip and flip every piling with no bite, but skip a bait on the back side of a piling from the side and get clobbered. Those fish get used to baits coming from the back to the front, but rarely see baits coming from the side or from the front to the back.
It's a lot of fun when you figure them out. It's a lot of fun too to fish behind guys and catch 'em.