Make sure all of your email invitees check their email inboxes frequently, and that you're using the address they use most frequently, in case they have more than one email account. Be prepared to follow up by phone if you do not hear back from a guest.
Be familiar with the options, such as: Do you wish for your guests to see the entire guest list? Do you want to keep their email information private? This is especially important if you are arranging a party for friends who may not know each other yet, or other mixed settings.
Be sure to include all important details in the Evite: the location (and directions), dress code, reason for the party, and RSVP instructions. Be sure to also include a personal message.
Proofread, proofread, proofread!
Follow up two or three days in advance with a reminder email. Since your guests won't have a paper copy to stick to the fridge, they'll appreciate a little note in their inbox so they don't forget.