Hi Newbie,
I haven't been out fishing on Lake WA since April, but I have been talking to a few folks fishing it lately, and I have been walking the shore a lot since I work next to the lake.
Both smallmouth and largemouth are spawning right now, but with this weird spring storm moving through today, they may pull off for a few days? If you don't find spawning fish, throw deep-diving crankbaits in 10-15 feet of water. Look for dock areas with isolated weed beds and/or large logs. Gravel bottoms usually help this time of year, too. I just mentioned crankbaits for the sake of covering water and seeing more of the lake, but jerkbaits, tubes, and senkos would be good bets, too!
The channel between Mercer Island and the east side of the lake (AKA "East Channel") probably has the largest concentration of fish in the lake, so if I was new, I would start probing this entire area. Fishing under the I-90 bridge is heavily-pressured, but it is also a very solid spot for catching.
If you feel like running up north a bit to see how the boat works, check out the docks in Union Bay and anywhere in Portage Bay for largemouth.
Good luck... and you have to tell us how the fishing is!!!
Chris