I hope this won't seem like a strange or uninformed question, but...

Is it possible in a bar to order a "tapas" as opposed to "racion" of something? If so, is that what you ask for?--e.g. "una tapa de queso manchego?" I suppose it's easier when you can order an amount of something--e.g. tres croquetas. I ask because sometimes when I'm traveling alone I'd like to have a snack at the bar (other than a pincho de tortilla--which I like, but sometimes you want something else!)but don't always want an entire racion of something.

liz49 writes: Exactly! I often order media ración of anchoas o boquerones or whatever when I want to sample a bit of this and a bit of that.
So, you may order una tapa, una media ración o una ración of whatever you see on or behind the bar.

I have found that some bars only serve tapas at the bar. If you are seated and there is table service, they may only serve raciones and media raciones to the tables. But it doesn't hurt to ask! Also be aware that some regions don't do tapas so much. Last summer in Mallorca, we found that their traditions are a little (or a lot) different than on the mainland. Still awesome food, though!

Liz, you can always make friends and share the racion.
-OhMike (trying to think out of the box).

You can order either tapas or raciones (or medias raciones in some places). You should usually find a big board with all that the place offers, and also you should look behind the bar as Eddie said.

In some places the tapas are not sold. They are offered gratis when you order a coke, a beer and so on.

Hope this helps

Fernando

As Fernando says, it varies a lot for each bar or town.
In Salamanca for example, you can look at the long 'barra' full of tapas, and you choose the one you want, or you can ask what they have. Here the tapa is a really small one (you need 4 or 5 to have a meal), and you have a a small price over the drink if you add the tapa. In Granada is similar, although you can get also tapas for free.
In Madrid, it's normal to get a small tapa for free, but normally it'll be from the cheap ones (bravas, olives, ali-oli...). Try to ask for 'medias raciones'. The idea of making friends is also good..The best number for tapas is between 4 and 6 persons.