Janie - it's pretty exciting when you decide when you are going to TTC. I started collecting baby stuff as soon as we decided to start. I went nuts on ebay and would buy the odd special here and there.
Don't go too crazy on the clothes as you will get given a lot with your first baby.
I wish that I had thought more about getting my house right for the baby. We left renovations until after she was born and it was pretty hellish. So if there's anything you are wanting to do with your house, do it now and get it out of the way.
As much fun as it is to buy baby things now, maybe just start putting money away so that when the time comes, you have the cash there to buy the things you want and need.
We took 12 months to conceive Gabby. For a while there, I was worried that we couldn't have children and was getting really depressed looking at all the baby stuff I may never get to use. Not that I am wishing anything bad on you, but sometimes it can be hard if you have collected too much stuff before you get that BFP.