Honesty is your best bet, but leave out the gory details. There could be many reasons behind the desire to end a relationship, such as, lack of chemistry, noncompatability, lack of romantic connection, and separate goals. A mature person will accept the reason and move on. There are no set rules as to whether you should break up over the phone, in an email, or in person. Respect, however, dictates doing so in person. It is highly likely that you will date a number of people who will not be your ideal match (nor will you be theirs) before you find the love of your life. As soon as you recognize that your date is not your ideal match, stop the dating process. When the person you’re dating recognizes that you are not a match for them, they will (hopefully) stop the dating process.
Still need an example? “Thank you for the opportunity to spend time with you. I have enjoyed getting to know you. I’m dating to find my ideal partner and I am not feeling the way I know I will feel when I am dating you. I want to end our dating so we can both keep dating others and find our true loves.” Its okay if you think this approach is corney or unmanageable. It is only an example and you must find your own approach.
As the song says, “Breaking up is hard to do”! And it is. Prepare, not only what you’re going to say, but the setting in which you say it. Prepare for a variety of reactions. Do not do this in a public place as reactions, such as shock and anger, may occur so you need to prepare yourself as to how you will respond. Avoid arguing and stick to the facts. However, be kind and understand that they may have felt better about your relationship than you.