First, cry if necessary! It is ok and quite healthy to cry over the ending of a relationship. Rebounding is usually a way to heal after a long term, serious relationship; so more than likely there will be some tears.
Second, when one relationship ends, process it fully; understand the part you played in the break up. Figure out what you would do differently in the future.
After you have processed everything and gained what you need to gain and left behind what you needed to leave behind; it is time to "date" yourself.
Go out and enjoy you! Go see a good movie, eat at your favorite restaurant; buy a new outfit and shoes and make yourself beautiful/handsome. It's not until you feel good about you that you can be good for someone else. This step may take a few weeks or a few months; maybe longer depending on the situation.
Next, now that you feel good about you, ask yourself a simple question, "Do I have to be in a relationship now"? Depending on how you answer that question, you may be ready to date again.
Last but definitely not least, whenever you choose to date, date for the right reasons and be happy!