Until you have the cover, the only thing you can do is talk about the book any place you can. The cover is sent to you. Have a cover release on the various venues. Find some blogs to visit and talk about your coming book. Plan for a release.
If your publisher puts the book up for pre-order advertise this. People can buy the emectronic version and have it delivered when it's released.
Look at promotional materials that can be used as giveaways. There are hundreds out there. Pens are always good but something unusual that suits your book can always be helpful. Use your imagination. Perhaps make book marks or have parts of your book to use as teasers printed and turned into a booklet.
Don't just sit back and wait for the readers to discover you.