If you're like me, then a good deal of your Chinese interaction takes place in shopping situations. Here's some stuff I use all the time (and didn't find in any of the books):

• Wǒ zhǐshì kànkan 我只是看看 = I'm just looking
• Ná zhège de yíbàn 拿这个的一半 = I'll take half of this
• Yǒu nǎ jǐ zhǒng? 有哪几种? = Which (several) kinds do you have?
• Ná zhè zhǒng 拿这种= I'll take this kind
• Ná wǔ kuài qián de 拿五块钱的= I'll take 5 yuan's worth
• Ná wǔ kuài qián de zhè zhǒng 那五块钱的这种= I'll take 5 yuan's worth of this kind
• Yǒu méi yǒu zhuōzi mài? 有没有桌子卖？= Do you have tables for sale?
• Wǒ yào kǎolǜ 要我考虑 = I want to think about it

I'm using that ná 拿 all the time now because that's the most common verb I've heard when I "tōutīng 偷听" ("eavesdrop", lit. "steal + listen") on real live Chinese people buying stuff. The subject "I" is just assumed. In that last one, "Yǒu méi yǒu 有没有[something] mài 卖," I have no idea what's going on with the grammar there. I'm sure there are other ways of saying the same thing. I usually just stick with a plain old "Yǒu méi yǒu 有没有 [something]" and it's assumed that I want to buy it. But, I've actually had to tag that "mài 卖" on there before, for example when I wanted to buy bike oil instead of just having the guy lube up the chain. If anyone has useful shopping vocab that is out of the normal phrasebook scope, please leave it in a comment below (I guess it's on the side in this current layout).