If you're planning to sell your home, and it's kind of an old home and shows this, you might be considering upgrading parts of the house to make it more attractive to buyers. In some cases, this is a good idea, but there are times when you don't want to make any major changes before you sell your home. It's best to upgrade the clear-cut problem spots and leave the rest alone. Now you just have to figure out what those spots are.
Safety or Code Issues
These are the big ones, the things you need to upgrade so your house will be up to code. Faulty wiring, lead plumbing that was never replaced, gas lines that look older than the house—all of these need to either be upgraded, or else you need to be prepared to sell the house for a very low price because no one will want to buy it unless they can fix it up. And they're not going to want to buy it for a high price only to have to spend a lot more to fix everything.
Safety and code issues aside, you generally don't want to upgrade major things, like the kitchen, just for the heck of it. There's no guarantee you'll get your money back in the house sale price. You're better off selling the house as is for a slightly lower price than upgrading and having to bring your higher price down over time.
If the upgrade is relatively cheap and small, then you might want to take care of it if doing so makes you feel better. Maybe there's an old tile on the bathroom floor that's just so scratched that you can't stand people seeing it; replacing a tile isn't that bad. But again, expect that you might not get your money for the upgrade back when you sell the house.
If your desired upgrades involve any sort of paint or solvent that could leave residual fumes, avoid doing it. The fumes could turn off potential buyers if the fumes are still around when people come to see the house.
You might have impeccable taste in upgrades, but whoever buys the house might have different tastes and want to redo the whole thing. That can lead to their trying to bargain you down on the house price. Because you don't know what the next owners will want to do with the place, avoid doing major upgrades not related to safety or codes and let the new owners have at it after the house sells.
If there are items you really want to upgrade anyway, talk to a real-estate agent first. The agent will have a better idea of what's selling in your area, and you can base your decision on the agent's information.