You should be upfront about your beliefs. You aren't ashamed of your religion, so don't treat it like something shameful. Telling your date you're a Christian does not need to be like dropping a bomb, or even bad news, on someone; however, both of you have a right to have that information out in the open. Saying before or on the first date that you're a Christian--and stating clearly what that means to you as regards dating--means that you've clarified your values and given your date the information she needs. This may also invite her to clarify her values with you and help you better determine your compatibility; you may even find that you hold very similar beliefs.
When you state your closely held beliefs, it is your responsibility to live up to them. Respect yourself and anyone you're dating by holding firm to your beliefs. Dating, especially as you continue to see someone, may come with a host of temptations and invitations to violate your values. Sticking to your beliefs reinforces them and allows you to feel good about your decisions.
If you do compromise your beliefs, it is important to take responsibility for your own actions. Blaming the person you're dating, especially if she has different beliefs than you, is both unfair and unproductive. You should feel open enough in your communication to address these issues as they arise, and, if you don't feel comfortable communicating, you're probably not seeing the right person for you. However, you might lose someone important to you by shifting blame onto her.
Respect her beliefs
Most denominations of Christianity have an element of proselytizing. While it is perfectly acceptable to share your beliefs with someone, even and perhaps especially someone you're dating, it is also important to demonstrate an appreciation and respect for her beliefs and values, whether she comes from another faith tradition or from a non-religious background. Proselytizing in a dating situation can be seen as just another form of seeing the person you're dating as a project, and you should instead be focusing on finding someone you can love the way she is and who can love you for you are. The golden rule applies especially when dating: Respect her and her values and ask that she respect yours, as well.
One of the easiest ways to alleviate many of the tensions Christian men face in dating situations is to seek out women with similar values. Whether from within your own congregation or someone you meet at a Christian singles' event, dating another Christian means that you've both already dedicated yourself to a similar set of goals and relationship values, and you can pursue these together.