Summarize this article in one sentence.
Spa parties typically involve just a few close friends because of space limitations. You want to make sure everyone can fit in the “spa room” without feeling crowded. If you have several rooms to devote to the spa — maybe one for mani/pedis, one for massages and one for facials — you can increase your guest list. Once you know who you want to invite, check with them to find a date when everyone is available. You will also want to confirm with parents or roommates, as well as siblings, that it is okay to have a sleepover on the chosen date. You don’t want the soothing ambience of the party interrupted by their plans. If you don’t want to have your siblings or roommates involved, ask them politely to stay in their rooms or go out for the night. However, it is often more fun to include everyone. Then you don’t have to worry about them disrupting the party. The best parties not only have a theme, but they have a plan. Know when you want your guests to arrive. Make a schedule of what you will do, what time you will do it, and where the activity will take place. By planning the evening, you can make sure everyone has a chance to do everything. When planning activities, be creative. You can have as many or as few activities as you like. For example, you might just want to do manicures and provide lots of polishes, nail decals, hand creams, and hand massages. Or you might want a full-service spa with manicures, facials, massages, meditation rooms, and a healthy-food café. Once you have planned the activities, you can make a list of everything you will need for each activity. Some things you will supply, but your guests can also be asked to bring some of their own items. For example, you might ask them to bring their own robe, towels, and brushes, as well as their favorite lip gloss, lotions, candles, and music. Invitations can be sent via regular mail or email. Either way, choose spa-themed invites featuring a picture of a slipper, an eye mask, nail polish bottle or other spa-related graphics. Include the theme, date, time, location and what your guests should wear. Include the list of items you want them to bring. Let them know how to RSVP.  Evites and digital invites are an easy way to quickly reach all of your friends. Several free online services allow you to design an invitation, send it to friends and tally responses all in one place. You can also easily create private events and send invitations via online communities, such as Facebook. You know what your guests are bringing, now it is time for you to get your own supplies. Large discount or warehouse stores, as well as beauty supply stores, will give you the best prices. Pick out some bright nail polishes, fun face masks, soothing tea bags, scented massage oils and other supplies for your planned activities. Imagine the perfect spa and try to replicate it. Remember that you must have enough supplies for all the guests. Small changes can turn your home into a relaxing spa. The key is to create a calm, quiet environment. Dim the lights. Place scented candles around the rooms you will be using — lavender and sandalwood are particularly relaxing scents. Play quiet music or sounds of nature, such as the sounds of the sea or rain forest. Serve pitchers of ice water flavored with lemon or cucumber slices.  A big part in creating a calm environment is getting rid of clutter. Make sure your home is tidy and clutter-free so your guests don’t feel overwhelmed by “stuff.” Make a poster of the services offered and post it outside the spa room. If you are using several rooms, make a poster for each room explaining what is offered inside. Neck and shoulder massages can be done almost anywhere. Simply have a couple of straight-backed chairs available.

Summary:
Make a guest list. Choose a convenient date. Plan the evening. Make a list of needed supplies. Send out invitations. Make a store-run. Create the spa.