First make a list of the friends you think will enjoy this. Keep it to a number that will fit comfortably in your space with room for nibbles, seating, glass wear, tasting sheets, etc.
For your first event have each guest bring one bottle of wine. Delegate each a white varietal including Chardonnay, Riesling, Pinot Gris and an aromatic wine such as Gewurztraminer, Muscat, or Viognier. For red wines Merlot, Cabernet, Pinot Noir, and Syrah will work best. Make sure you have 2 glasses for each person, spit cups, water, and neutral crackers or bread to cleanse the palate between wines.
There are some great resourses on the web for tasting sheets to score your results for the evening. One of my favorites is http://recognose.com/ which has a number of downloadable tools and tips to help you plan your tasting. I have developed a sheet for you to use to help identify aromas and styles as well http://wendycrispellwine.com/Wendys_Aroma_folding_card.doc .
For help with indentifing aromas make you own wine aroma station! Simply assemble a group of aromas from your own kitchen. Spices (clove, nutmeg, allspice, pepper) fruits, jams, herbs, honey, coffee, fresh fruit and others aromas are in most everyones pantry. Put each scent in a small glass covered with plastic wrap. As your tasting pass around the scents and see if you can identify any in the wines of the evening.
Learning about wine is fun! It can also turn into a lifelong hobby that you can share with friends and family! Enjoy!