One possible suggestion: In the parts that you think there may be too much description but you still want to keep the thought, look at it all and try to think of a word or sentence that would summarize it. Try to find those perfect words that uncannily catch the essence of what you are trying to say. It's very difficult and challenging (I suck at it!) but when someone takes the time to do it, it is very enjoyable for the reader. How many times have you been reading a book and then stopped, awed by someone's perfect word or phrase? Aim for that.
Depends on what you're writing. If it's action/adventure then things don't have to be described in too much detail. If anything, go into the least detail as possible; you have be a little vague. Fast-paced means less descriptions and more explosions. I don't want to know about what shape the mushroom cloud was when I can hear about what happens next. If it's fantasy, you'll need a little more decription, especially for things that are fantastical in nature. For example, if you're introducing a new concept of the elf or a fairy or something, it's best you go into detail based on their habits, their appearance, their culture, or whatever. Romance... I don't read romance, so don't take this too seriously. However, I assume that would take a lot more description based on the looks of others and how handsome/gorgeous/whatever the hell their boyfriend/girlfriend/crush is. Same with drama and all the other woman-pleasing genres (jokes, not all women are into this). Personally, I can't stand description and it shows in my writing. A lot of the time, my character will appear in a room and that room will only have two sentences dedicated to it, at most. Sometimes I don't even decribe the room. I might call it "empty" or "furnished" a lot of the time. I like to keep all those words to a minimal. And I even know a girl who just skips a lot of the description and just reads the dialogue. She's the only person I know who does that though. It all depends on what you're writing, in the end.
Too much much can be as ambiguous as not enough. I would think that upon proof reading your work, you find yourself even asking the question, is this too much? Then that might be your indicator to rewrite. I like to use the character's actions, thoughts and dialog as the tool to describe, as oppose to narrator describing the scene or setting. Also detailed description is not necessary in nearly all things. Why? Because the reader will "fill in the blanks" for you, as they read it. The reader will imagine the setting and description of the characters, and actions on their own, all the writer need do, is coax the reader in the general direction, and then allow the reader to fill in all those details we may feel necessary to list. Do your best to be imaginative, and descriptive without giving step by step instructions. If your character is climbing a tree you do not have to describe what a tree looks like, nor how long it took for it to reach it's current hight. All you need do, is describe the character's efforts of climbing, and throw descriptive phrases to give the reader a few hints. The rest will happen naturally, that is so long as the writer has not interfered with that natural process that is.
