(I wrote all this, then realized Pastrygirl said many of the same things, so I guess I'm echoing her:)
I love shopping at the Rack and I seem to do well there - many of my best WIWs here are Rack scores. But, my local Rack is a big city one that gets true designer items from the downtown Nordstrom, and when I go to the suburban ones nearby it's a different experience.
My technique to not get frustrated and overwhelmed:
1. I only look in the designer-ish section of the store. There are racks of Vince, Theory, Helmut Lang, etc. The Rack prices put those in range of my budget (barely) so I only shop in that area. And I make myself ignore the racks from designers that don't fit my style as well (anything feminine or boho) even though I'm sure there are treasures there if I look hard. Similarly, I usually only look in the designer shoe section. The other section has plenty of lovely choices too, but the choices will overwhelm me and I have very picky feet. I just do a quick skim for anything that is fabulous _and_ a huge bargain.
2. I focus on the odds and ends of true designer things, all jumbled on a few racks and sorted by size. This is where I've found awesome things like a Helmut Lang tux jacket for $50 or a Rick Owens turtleneck for $25. Oh, and like Pastrygirl, I look in *all* the size sections here.
3. I don't even let myself near the clearance, juniors, or lingerie. Even though I'm sure there are some good things there. It'll sap all my energy. (One exception is when they advertise their big clearance, and a lot of great things move to huge new clearance racks.)
4. I only let myself try something on if it's something I would definitely buy if it looked perfect. And it rarely looks perfect on, even so. I am very very picky about what I buy. Or I buy things, ask my boyfriend for an opinion, and return them if they aren't awesome.
5. And, the one I don't do as well on: I try not to let an amazing deal sway my choice. The Rag & Bone knee-high Newbury boots showed up once for something like $100 instead of $600, and looked amazing, but the heels are still too high for me. I was soooo tempted.
6. I'm trying to figure out when they shift merchandise from Nordstrom to the Rack. Sometimes I show up and I'm blown away (there was one time I found so many amazing shoes - nothing I wanted luckily or I'd be broke).
And now I REALLY want to go to the Rack. Maybe after work today.