Cross dressing is when someone dresses up in clothes that are better suited to someone of the opposite gender. If you are a man who enjoys cross dressing, you will wear feminine clothing and accessories, while a woman may wear a suit. There are many different reasons for cross dressing. It could be just as a bit of fun, while others may find it a turn on to feel the lace of French knickers on their body. Finding a partner accepting of this is important, as not only will they understand your interest but they will also help however they can.
Many feel that, as they cross dress, they can simply raid their partner's wardrobe. However, many may feel uncomfortable if you do this without asking, so make sure you do. If they allow you to and the clothes don't fit you properly, don't force it. Your partner might not forgive you for stretching their favourite figure-hugging skirt so that it fits you better. Why not buy some clothes especially for you and bring them with you?
On another note, some may be more than willing to share their clothes with you, even telling you what you should and shouldn't wear. This might tie in with sissyfication, for those wanting a more BDSM relationship, though being treated like a woman isn't a necessity. If you would rather just wear the clothes, make this clear to your partner. They will not make you do anything you don't want to do, so telling them your limits will make your time together far more enjoyable.
For some, they feel that cross dressing is as simple as wearing ladies' underwear underneath their normal every-day clothes, while some prefer to wear a dress, heels, and a wig. Experiment with what you feel comfortable in, and don't be afraid to try something different. You may find that you enjoy it even more than you thought!