This is an TL;DR excerpt from a post by Luke Prosser of LearnMusicTech.com on how to get better mixes done in the bedroom:
Here are 14 quick, easy (and cheap) tips for prepping your room:
1) Don’t waste money on expensive equipment
First of all, don’t jump into buying tons of acoustic treatment before assessing your space. Also, don’t assume that better gear is the solution, either. High-end audio interfaces and monitor speakers will not solve the problems of a poor-sounding room. The recordings will be limited by the acoustic performance of the space and, as mentioned, speakers are only as good as the room that they’re playing into. Monitors should also be relative to the size of the space that they inhabit. If you have a smaller room, use smaller speakers. Large monitors are pointless in a small bedroom and, more often than not, actually have a negative impact on the mix.
2) Use reference tracks
If a professionally mastered balanced track is resonating at a particular frequency, you can make a pretty sure bet that it’s the room that’s causing the issue, not the master. By flipping back to your reference throughout the mixing process, you can assess the performance of your own mix and push or pull frequencies to adapt accordingly.
3) Get away from the walls
Try moving your setup away from the rear wall and further towards the centre of the room (although not the absolute centre, as this will also give an imbalanced perspective). It’s also a good idea to avoid placing the speakers directly in a corner to avoid frequency build-up. As a general rule of thumb, many people advocate the ‘equilateral triangle’ rule, where you position yourself equidistant from both speakers i.e. just within the third point on the triangle. While I don’t have enough space to fully break down monitoring positions and speaker placements in detail in this article, a quick Google search will pull up some great articles on the subject.
4) Avoid corners
Applying absorption to the corners in your room will provide one of the biggest returns on investment. This will reduce much of the high-frequency ringing and flutter echo. Placing bass traps in the corners of your room can also mitigate against low-end build-up.
5) Avoid parallel lines where possible
The majority of bedrooms are cube-shaped, which is one of the worst possible dimension combinations for acoustics (cubes certainly contain plenty of 90 degree corners!). Any resonant frequencies or flaws within the space will be magnified further in a cube, so anything that can be done to avoid this will have a major impact.
6) Absorb low end
Big, heavy, cushioned objects help to absorb bass frequencies. Being in a bedroom, a mattress is actually a big advantage. Effectively a huge sponge, a mattress will help to absorb many of the low-end frequencies that can build up and resonate in a small space.
7) Cover your windows
If you’re in a bedroom, it’s likely that you have a window on at least one wall. Frustratingly, glass can create bright ‘slapping’ reflections that lead to an inaccurate view of the top-end. Consider closing curtains or covering windows altogether with absorbent panels.
8) Keep your bookshelf
A well-stocked bookshelf can act as a useful diffuser. It’s not the same as a real diffuser, but it’s a decent home brew option, particularly if you already have one in place!
9) Monitor at low volume levels
If you have an imperfect room (which is pretty much a guarantee in a residential property), mixing at low levels can reduce the sonic impact that the environment has on the track when listening. At a lower amplitude, less undesired reflections will be created and the strength of resonant frequencies will be reduced.
10) Make use of headphones
Although I can’t recommend solely using headphones when mixing, they’re a boon for home recording when you’re working in an imperfect environment. Headphones isolate the sound, so there is no opportunity for it to interact with the space around you before reaching your ears, thus eliminating the impact of the room.
11) Isolate your speakers
Not only is it a good idea to move your monitors away from nearby walls, it’s also important to isolate them from contact with any other reflective surfaces. There are a number of ways to separate your speakers from other surfaces and minimise these unwanted resonances and reflections, such as speaker stands, desktop pads and desktop stands.
12) Make use of the closet/wardrobe
Try opening up your wardrobe while mixing to break up any parallel walls and get some extra absorption to prevent reflections. In addition, why not try adding cushions, pillows, blankets, towels – essentially items that you may already have hanging around the house – to shelves to improve this effect? You can even fix additional acoustic panels to the inside of the doors for added diffusion.
13) Leave the room
This one may sound a little left of centre, but often you can actually get a more balanced impression of your mix by turning up the volume and listening outside of your room. Try going out onto your landing, your hallway or down the corridor and take a listen from a different perspective. You may find that certain flaws in the mix begin to jump out and become more obvious from this alternative position.
14) Leave the house
Continuing from Tip 13, actually getting away from your studio altogether can be extremely helpful in getting a better overall impression of your track. Bounce it down and put a copy on your smartphone. Go for a walk and take a listen on some headphones. Take a drive and test out the mix through your car speakers. Take the mix to a friend’s house and test it on their system. You may even know other producers that have alternative setups, and you can also send your track for feedback.
Thought I'd share as there's some really good info here!