How I shop at second-hand stores (ie Goodwill, Salvation Army, etc.): I call myself a "scanner", I head to each department (furniture first) and scan what I see. If something jumps out at me, I stop...I'm not a look-love-linger sort of shopper, I'm pretty fast. Don't forget to look on the bottom shelf either. As my eye improved (over time), I see the potential in furniture and accessories in a jiffy.
How I shop yard sales and garage sales: Now it has taken me a while to get comfortable with this type of shopping, it's just my personality, but I hesitate going up to a complete strangers home and start rifling through their stuff...but realistically, the are having a sale and have it out in the yard/driveway etc, get over it, Michelle. They are just trying to get rid of their stuff, and make a little money while they're at it. Simple. And I have found some great stuff. Confession though: my MIL has caught the 'yardsale' bug so she is usually with me, so I feel more confident. Shop with a buddy!!!
Same thing as if you were in a store, scan, scan, scan. Don't be afraid to leave empty handed either, if you don't see anything, walk away.
How I shop Estate sales: Shopping estate sales is a lot like yard sales, but the stuff is usually better, and the prices are a little higher (not much though) and you need to be there super early. All the good stuff is gone if you go late. Usually, there is a service that is handling the estate sale (which accounts for the higher prices)...there are different associates that help around in the different rooms, and a check-out area when you are done. I do, however, and this is my personality again, feel a little sad at estate sales...you know someone has passed away and this is their children thinning down the household, it's just sad. So I do sort of mosey through the home, room to room keeping my eye out for good stuff...again, scanning. Also, estate sales are where I find a lot of great vintage jewelry.
How I shop Auctions: Now I am fairly new to auctions, but find them to be quite fun. I've only been to estate auctions (sad again, I know!) versus Auction Houses. Estate auctions can be found in your newspaper, or online. First, get there a little earlier than the scheduled time....and plan to stay late, it's an all day affair (and I recommend leaving the kiddies at home for auctions). I walk around and find the things that I think I want to bid on...you have to be stealthy and quiet. Don't visibility show interest in anything or you'll call other people's attention to it and the stakes could possibly go up.
Whisper a lot. If you are with your shopping buddy and need to share your excitement over something, you can, just whisper. This is the time you find out whether you even want to stick around or not.
The auction can begin, you've got your mental list prepared from doing your recon earlier, and you can bid on said items. I do have a cut off point though...I let things go (ie lose) if it's beyond it's value, or what I'm prepared to spend...however, I have 'won' things for very little and known the value is much greater....that's the fun part. The other fun part, and I'll throw this one in there for free, is watching what other people will bid on....it's the 'people watcher' in me that finds it fascinating to see what people bid on, for example, a box of plastic ducks...I know, I know, each to their own....they've probably done their mental list and plastic ducks was on it!
I have seen crazy bids too like, a crappy set of beat up old wicker furniture on it's last leg go for more than a solid oak dining table and chairs in excellent condition...I've seen people argue with the auctioneer to the point the law might be called....you just never know what will happen at an auction and it's a thrill.
I look for things that are well made, classic pieces that have stood the test of time. Even in accessories, I avoid trendy collectibles and look for timeless pieces that represent an era.
Some weekends are good some are not, but if you go frequently enough and hone your eye, you will find pieces that you'll love. Keep an open mind and visualize what it could be.
And one more thing, don't you think things were made better 20 (even 10) years ago than they are today? I figure too, if it's lasted for 10, 20, 30, 40 years already...it's going to keep on going. Money well spent.