I windowshop with friends, I do serious shopping alone. Knowing that someone is waiting for me irritates me.
Like so many here, I loathe crowds so you'll never find me at sales. If I so much as see a 3 person queue for the changing room, I put everything back.
If I'm seen the catalogues of a store / boutique that, I'd have have picked out a few pieces and will directly ask the sales people to bring it for me. I take that waiting time to browse quickly for anymore interesting pieces so that they can bring those for me while I'm trying on the first set.
I don't really compare prices. If I like it, I buy it immediately.
I hate rummaging in those racks / bins where they have the "sale" goods. It's usually not organised and I get a headache. I like stores with neatly arranged racks and shelves and vast spaces. Yep, I'm very claustrophobic.
Whether or not I go into a store depends very much on the interior decor as well. I tend to go into places that are clean, wide and minimalistic in design and decor (applies also to the clothes). If it's got funky decor, weird lighting and loud music, I won't go in.
If I'm not sure whether I like a piece of clothing, I usually don't buy it.
If the sales people are rude / snooty / irritating, I walk out of the store without buying anything.
When it comes to makeup and fragrances, I'm a sucker for packaging.
I usually need a coffee and snack after shopping so that's when I'd have arranged to meet up with friends!