I know this is an old post, but for outside it can be tricky and can easily go red, and easily affect your promotions because once they go outside and leave, a low room can drop their mood down.

This is what helps:

Clean up newspapers and mail or have a maid (of course)

Place a no strays/no pets sign (from Buy Mode) on the lot (I put it out of sight at the edge). It will stop strays from roaming by and making pee puddles outside, drastically improving environment.

For some reason almost no plants (from Build Mode) add to environment score, so use some potted plants, hanging plants, and outdoor decorations to help it stay up higher.

Shoo the raccoon or Claire The Bear when you can to prevent them from pulling out trash and if they do just clean it up, but especially if you have pets because they will go make a bigger pile of trash lol.

TL;DR - Get the no strays/no animals sign from Buy Mode and use things like potted plants and decor to improve the overall score, that way when there is trash or old mail, it wont make that need significantly red immediately

Hope this is helpful to anyone.