I can think of a few good ways. If you haven’t already, giving it a new paint job is a good place to start. It’s also a good idea to get it professionally washed and see which of the outward-facing fixtures can be painted and/or polished. You’d be surprised by how much nicer a house can look if the metal window frames are freshly-cleaned and polished, for example.
It’s also a good idea to look at all the concrete surfaces that surround the house. Examine the patio, the driveway, all the walkways, etc. All that concrete may look old and faded now, but getting those surfaces power-washed can fix much of that problem. Or you can take it a step further and reinvigorate those surfaces with different coatings. Take a look at the metallic epoxy flooring showcased on this website for an example of what can be done.
Your lawn is also a good point to focus on. How well-trimmed and vibrant your grass is can have a big impact on the overall visual appeal of the house.