PP brings up a really great point about lead.
We bought a 1950's ranch that was in the process of being remodelled, so it was gutted down to the studs and subfloors when we took ownership. Any home from that era will need to be tested for lead when a contractor is brought in. We had to come up with an additional $12,000.00 for the workers to take out the windows that we were replacing and wrap them in plastic before they put it in the dumpster. It doesn't seem like much additional work or supplies, but OH was it a major expense that was not expected.
Contractors will want you to know what you want. I suggest pinterest and picking up books and magazines to find inspiration. Try to keep some of the detail that you don't see in new construction- built-ins, arches, woodwork, etc. I think that charm adds to a house.
Also, be sure to renovate for your life in the home. Do you plan to stay there for 5 years, 10, or 20 years? If it's a shorter term then I'd focus on what is going to entice buyers- kitchens, bathrooms, more neutral colors, a breath of fresh air to the house but don't go overboard. If you plan on being there for a long time think about what will suit your needs best- adding a bathroom, converting 2 small rooms into one larger, more custom options, etc.