Make sure your house is very clean and organized, not to much, but the kitchen and bathroom should be very clean! And organized.
I get a lot of compliments of girls about how clean and organized it is at my place.
One of the first things girls notice when walking into my apartment is in the hallway there are some shelves, some are empty, the bottom one have bottles of soda on them. But on eye height, is my liquor collection. This is a couple of bottles of good whiskey, some bottles of wine, vodka and rum.
The first thing they see in the living room, is the fruit basket on the dining table (of course with some fruit in there). Then there is my guitar casually placed against one of the seats in the living room. I do not yet have any paintings on the walls (just moved) but I do have the flag of my country hanging there (left over from my moving in party).
When they walk further into the living room, they see the decoration of my balcony. Even though it rains most of the time in Dublin (compare it with Seattle), I decided upon a Hawaii theme on my balcony.
Then when they walk into my bed room, there is no clutter, the first is a rack with my shoes, not to many (about 10 pair, dressed up shoes, sneakers, etc), some shoulder bags (casual and business) and maybe a pair of pants and a sweater of the day before. Because lets be honest, it shouldn't be to tidied up.
After that on the dresser in my bedroom are two records which I really like, my collections of watches in a leather box with glass cover and a camera, pointed at the bed, which not one single girl mentioned(!).
Then she will the there are a few books by the side of my bed. The bed is always made and, when it's evening, I make sure that the curtains are closed. And everything matches! So the sheets, the curtains, the color on the floor and walls. Most of these things are cheap to get. I also have a 2nd set of pillows on my bed, they serve no other purpose, then showing girls that I have some style. Because they love that kind of stuff.
My bathroom (en suite) is also prepared. I have a rack specially for the bathroom, with everything organized, the things that I don't use on the bottom and the things that I use a lot, on the top. It is easy to grab, big bottles in the back and the smaller ones in the front. There are some facial wipes in there, baby body lotion (girls like that after a shower sometimes) and the hand soap is on the sink. Also a clean towel to dry their hands is always there.
By the toilet side, there is a box of wet wipes, matches (I don't like spray's, they smell even worse I think) and always two extra rolls of toilet paper.
A tip on keeping the bathroom shiny! After you took a shower, use your towel to wipe all chrome bits dry! Do the same with the sink. Also use a wiper to clean your walls and glass of the shower every day after the shower! This will make is easier to clean (so you will do it more often).
There hasn't been one girl (either friends or dates) in my apartment, without complimenting me and being impressed.
Basics: keep it clean and tidy, get some style, show what you like.