Forget everything you think you know about groomsmen. They don't have to wear a black-and-white James Bond-style penguin suit. They don't have to be your brothers. They don't even have to be men!. That's right, these days you can pick your sister, your cousin, or your girl best friend from grade school.

From groomsmen ...er...groomswoman gifts to bachelor party planning, here are four must-follow rules for female attendants:

Thou Shall Not Make the Bride Jealous

Even if your bride and your ex-girlfriend are best buds (in what world?), or you dated your ex 10 years ago, you cannot ask her to stand up on your side as a groomswoman. When your "best woman" starts weeping at the ceremony, people will wonder if those tears are falling because she's still in love with you. Stick to your sister, cousin, or longtime, non-threatening friend (non-threatening means not as pretty as the bride).

Thou Shall Not Make the Groomswoman Wear a Tux

She's just one of the guys, but she doesn't have to look like one of the guys. A simple black dress will differentiate her from the bridesmaids and she'll still blend with your boys.

Thou Shall Not Give her Gendered Groomsmen Gifts

This is the hard part of adding a groomswoman into your gang: you have to find her a groomsman gift. You probably shouldn't give all your attendants old-fashioned shaving kits as groomsmen gifts -- unless your groomswoman is part of a traveling freak show. Personalized poker sets and flasks make great groomsmen gifts and groomswomen gifts. Still can't find anything? Peruse bridesmaid gifts for girly gifts she'll love.

Thou Shall Not Make her Plan your Bachelor Party

Even if she's your best woman, don't let her plan your bachelor party. Hiring the talent or adorning the hotel suite with blow-up dolls might make her uncomfortable - especially if she's your relative. Talk to her about all the best man duties before she signs on. Assure her that you delegated bachelor party planning to one of the guys, but that she's in charge of everything else. Groomswomen are automatically invited to bachelor parties, so don't leave her out.

The only rule when it comes to your wedding party is to invite your supporters - those people who are happy you're tying the knot. Nowadays, you can have a dog, your grandpa, or your goldfish - it doesn't matter. Just make sure you thank all your attendants with well-appointed groomsmen gifts or groomswoman gifts!