1. For starters you should wait for a relaxing environment when asking someone out for a date. Never make that move in a tense environment. You don't want to come across as tense or stressed out. You want to appear calm and confident. It's important that everything should just flow smoothly.
2. Do not pop the question out of nowhere. The conversation should naturally lead into asking someone out for a date. For example, it would be ideal for both of you to have just finished talking about something that you both are interested in which brings comfortability and then an "Oh by the way..." is a perfect opportunity to ask for a date.
3. Be sure that when you ask out somebody for a date try to do something that you enjoy doing and are good at. This will increase your confidence both when asking them out on the date and during the actual date. Confidence attracts people towards you.
4. If you did get that first date then your next job is doing all of the right things to get the second date, right? So while on that first date, be sure to have the attitude of giving rather than getting. Try to involve activities that he or she would enjoy. Do your best to create the date around them, showing your attention, and making them feel special.
5. Last but not least, just be yourself when asking him or her out on a date. Do not try to act like someone else or pull those one liners. Trust me, being original works every time!