If you're living in a rental, there is only so much you can do in terms of updating/making it your own. That said, it still might be worth it. Paint, plants, and curtains can go a long way.
Paint the Walls
I have done this twice, an while you may need some helping hands, it's a go to option for updating any room. Landlord approval is a must, of course. Sometimes, this may not be an option. If not, it's okay. There are so many other things that you can do in addition to or in place of painting the walls of rented apartment or home.
Paint the Cabinets
I think every single rental that I have ever had has include some type of 1990's maple/oak cabinetry. It's pretty outdated and just not my taste at all. You'll obviously have to ask your landlord if it's okay, but painting your kitchen or bathroom cabinets is something that is entirely doable for those of us with rentals. It's also not incredibly difficult, although you will have to set aside a lot of time to complete this project; don't rush it. You can always tell in the results if a paint job was rushed. Some popular cabinet colors include white, various shades of gray, and deep navy tones. Which color you choose is totally up to you/what your space currently looks like, but I'd be sure to run the color choice by your landlord.
Use Removable Wallpaper
I helped a friend install this wallpaper, and it is pretty incredible. Although it is removable, she did still get her landlord's approval, just in case. She used a white and gold diamond pattern that has since been sold out, but it worked wonderfully as an accent wall for the entry area. Removable wallpaper is super easy to apply with two people, and it truly looks like a million bucks after it's up.
Curtains are one of the most underrated decor elements. It's worth noting that these don't have to be super incredible window treatments. Even simple curtains can make a HUGE difference, especially when it comes to bedrooms. I am going to make a bold statement; make sure that each bedroom in your rental has curtains. I always look for curtains that are quite thick for winter (as I live in Wisconsin) and then lighter counterparts for summer. That's another thing to consider with curtains - they are easy to change with the seasons, they can help block out both heat/cold and light, and they add so much style to literally any room.
I am going to be talking about this more this week, but plants are another easy way to add so much more liveliness, color, and style to a rented apartment. You don't have to have a green thumb either. I'll be talking more about low maintenance plants to add to your space on Wednesday.
Switch Out Decor
If you've been settled for some time and you want to refresh your room, an easy way to do this is to switch out the decor. Luckily, most decor is pretty affordable. A few purchases and a few switches can make this a really easy process. Be sure to also update picture frames with recent captures. Another option for a stale rental may be switching up your furniture layout.