Don t freak out. Here are 5 essential steps to make this a mistake free, anxiety free and hassle free project with a happily ever after ending.
1. Think about an inspiration board. It should include colors, textures, and photos of everything you love. OR Make things really easy and trot on down to the local family owned, nicer furniture store, you know the one, and talk to a designer. Yes, talk to a designer. They will sketch out your room and help you find the things you like. They will even come out to your home, at no charge, and look at your room in person. They can take an inventory of the items you want to keep and be sure they coordinate perfectly with your new purchases. The key to this is to have a plan and buy to the plan. This saves time and money because it eliminates mistakes. 
2. Establish a budget and stick to it. This will ensure there will be no financial surprises.
3. Buy the big things first. Prioritize your purchases so you get the essentials in the budget right from the start. This way you know the room will be functional. Buy your accessories and finishing touches last as your budget will allow.
4. Measure twice/ cut once. An old construction rule that works for furniture shopping as well. Measure your doorways to be sure whatever you buy can fit into the room and up the stairs. Measure the room to be sure the furniture will fit the floor plan. 
5. Making a list and checking it twice is also good advice for furniture shopping as well. Double check you color choices. The lighting in the store location can change how a colors looks. Bring home fabric samples to see them in your home during the day and night. 
Truly the bottom line here is PLANNING.