Because of the amount of food the Spanish eat throughout the day, the evening meal is a relatively small affair.
If you've been eating like a Spaniard (a light breakfast, a big lunch, and perhaps a light snack late afternoon) then you shouldn't be especially hungry when it comes to your evening meal anyway.
Your options in the evening are as follows:
Tapas bars will be full of people having a few light bites to eat in the evening. Click on the above link for more information on tapas in Spain.
A Full Meal
A full meal in the evenings in Spain is likely to cost quite a bit more than it would at lunch time, when the economical menu del día
is on offer. In the evening you will be forced to order de la carta
and will pay three times the price.
Ración, Media Ración or 'Para picar'
A racion is approximately the equivalent to four to six tapas, while a 'media racion' is equivalent to a little over two tapas. Para picar means "to pick at" (and is probably equivalent to a ración). These dishes are intended for a group to eat together. Raciones are always a plate of a single item - ham, cheese, calamares, etc and are too monotonous to eat on their own. If eating alone, go for a couple of media racions.