try as many as you can! for your first horse you need to find your perfectness match
definitely listen to the advice of the older and more experienced. sounds like a no-duh tip, but very important to get some help until you're confident you know what's what! you'll be thankful you did in the long run!
Ask any bad habits. Herd bound, pulling, cinchy etc.... When you go to try it ask that you can be there to catch it and saddle. So then you can see how he is to be caught and handled. Always watch the owner ride first! This allows to to ensure your safety. Some people think their horse is an angel when I would beg to differ lol ... don't just look for a great deal, normally with horses you are getting what your paying for. If you have only been riding a short while I would recommend a older horse 6+ age range. Horses personality can change with growth and at that age your most likely getting what you get.
Don't be afraid to reach out to others! If there's something you aren't 100% certain of make sure you ask someone with more experience owning horses.