Well, my parents have both been real estate agents for years and I worked in their office for a few years. So I have been exposed shall we say to the business.
I'm not entirely sure what to tell you about getting the most for your house - if you need to sell quickly, you'll do well to price the house well - don't overinflate what you think its worth. A good real estate agent will be able to do comps for you, etc. The sellers that have the hardest time selling often do because they are expecting to get much more for the house and won't come down in price. Your house is only worth what someone will pay for it - not what you paid for it or what you can add up all the money you spent on it, etc. What my mom always says is 'pristine sells' - the better you can make the house look, the better your chances are.
If you are painting, definitely pick neutral colors - painting the walls makes the house look newer & cleaner, and no one blinks at white (or offwhite) walls, but if you have outrageous colors, even not that outrageous, it may not mesh with the buyers tastes and then of course they will be mentally adding the cost/time associated with repainting in their heads. I am amazed at how much nicer a place looks with a fresh coat of paint on the walls / ceiling.
For the carpets - how bad are they? I personally wouldn't replace them unless they were really bad or really old and really ugly. Get them professionally cleaned though - you'd be suprised how good carpets can look after a professional comes through. When we sold our condo we did this - and though we had lived in the place 5 years and the offwhite carpets were original, my DH overheard buyers wondering if they were new. While you may feel unethical about putting cheap new carpets in, buyers won't pay more for your house because you put expensive ones in, so you would just eat the extra cost - better to let them make that replacement and choose the carpet quality themselves. If you do replace any, definitely neutral colors. I remember as a buyer when we bought our house last year being very turned off in one house that had brown rugs when the homeowner said 'oh the rugs are all getting replaced - same color' - While I'm willing to buy a house with old rugs and replace them, I don't want to buy a house that has BRAND NEW rugs I don't like!
You might want to have a friend come through and look at your house from a buyers perspective - there are lots of little things you could fix up or clean up to make the place look nicer that you may not notice anymore because they've become part of the background.
Oh, another tip - reduce the amount of furniture if you can. An underfurnished room looks bigger. Many of us stuff lots of furniture into rooms and that makes them look tiny - if you can store a few chairs or couches elsewhere and free up space it can help tremendously.
In general the best time to sell is spring/summer - the market cools down near the end of summer and positively becomes stagnant around the holidays (Oct/Nov/Dec) - most families don't want to move during the school year and no one wants to move during the holidays.
Anyway, that's all I can think of, I hope some of it helps!