Shopping for furniture stinks!

So, we have been married for 5 years now and just last year purchased our first piece of furniture. It was a mattress. Best investment we have ever made. This year because of family visits, etc. we are investing in a new couch that someone could sleep on, or has a bed. We've been looking at the classifieds to try and find something that we like and something that is comfortable, but how can you tell from the picture or the owners description? Or do you call and ask if you can barge into their house to look at it and sit on it? That seems so scary to me. Its a little easier in the store, but we will definitely end up paying more. So, help! I obviously don't have much experience purchasing furniture and need some guidance! (and now I'm laughing at myself, because that statement/exclamation seems totally ridiculous. Oh well.)