I've got a couple techniques to share. Why listen to me? I spend somewhere close to six hours a day in Photoshop, and have for the last 5 (10?) years. I'm not sure how I feel about that.
Good.
Let's go with good.
I expect (read: hope) you know the tools I'm showcasing here. They're pretty basic. We're talking wand tool, lasso, quick-select and other simple malarky like that. The idea here is to show you how to use and combine them in ways that will make you much, much faster.
Marquee
Less basic than the title might make you think.
Quick Selection
Consider yourself in good company if you didn't even know this tool existed, and in nerdy company if it's coming up in conversation at all.
Fixing Color Spill
Trust me, you want to watch this, even if you don't quite know what it is.
Tweaking out the Edge
Because 95% of the way there still looks plenty awful.