Souvenirs can be bought impulsively or a very well thought out purchase. They are the sort of show off things to say we've been here. It sort of depends on how you plan. If you want a nice set of Delft plates or some porcelain figures then you will have a pretty good idea of what you are getting and how much it will cost. If you are like me then I know where I'm going and I'll have a price range in mind and I'll look until I find something that jumps out at me.
I've learned one major thing about souvenir buying while on vacation. If you see something you think you like and are sort of on the fence about it and you know you aren’t coming back then buy it. If it is a unique item and you decide later you don’t want it they you can probably sell it for what you paid for it. Then again you may decide that you really were glad you bought it.
Here are a couple additional things I’ve learned about souvenir shopping.
I collect cloisonné or decorative pins. If I’m near a Hard Rock Café I usually pick up at least one. The thing about these pins is that they are specific to that Hard Rock and they are usually a limited run so if you go back a year later you won’t find it. This is also true of the pins you get at Disneyland and I’m pretty sure they are the same everywhere else. The thing is you can trade pins for different kinds if you aren’t happy with the one you got.
If you are in a heavily visited tourist attraction and there are several shops you’ll find similar but not the same item from shop to shop. If you have the time then look around for that item that really fits what you like.
I like t-shirts and I have a wardrobe of them and most of them are souvenirs from places I’ve been. T-shirts will eventually become rags. I’ve gotten to the point where I spend some extra money on the more permanent souvenir. In some places you can spend $20-30 for a t-shirt and maybe you can get a nice local artist painting or drawing for the same price.
Don't let the size of the souvenir put off buying it. If you want it and don't want to carry it with you for the rest of the trip then send it home. If you've put a hold on your mail then the post office will hold it for you until you get back. If you make arrangements with a friend or family member before you leave then send it to them and it will be there by the time you get home or at least a few days after you get home.