Nervousness is normal! Oh how simple it would be to ask someone out without being emotional or nervous. Here is the way. Pump yourself up by saying to yourself 'I deserve this person and nothing is getting in my way'. Don't over think this as you'll never get the courage once you think things over. Furthermore, spark the conversation up with her/ him and as soon as he/she is comfortable hook him/her with the question, just make sure it is only you two at that moment. Confidence is key to get the yes you deserve. Additionally, if you think you don't deserve her/ him you two will never last.
Despite the fact that you may be nervous, act confident and try to make your body relax. Ask her out via text or email if you have not gathered enough confidence to ask her in person, the latter would be better, however. Whatever, you say, try as much as possible to avoid the use of the word "date."