How do you love someone you hate? Too shy to use the word "hate"? Let's just say you strongly dislike their guts, shall we? The bottom line is they have ways and means that always rub against your grain. Perhaps they did something or are daily doing something that squeezes the ugly out of you. Love is the last thing you want to mention in a sentence with their name unless it's, "I would love to see___________ get <<insert painful thing here.>>As children of God, we feel the tug of the Holy Spirit rebuking us about those feelings and yet the fire won't go out, not for long anyway.
What to do?
First, find comfort that the commandment to love your enemy is not a call to a feeling. Emotions are merely the smoke that belongs to a fire. Douse the fire of not loving and the smoke will be gone too. So, what is love if it's not a feeling? It is a choice. Yes it is. It is a deliberate act of your will to behave lovingly toward your enemy. If you're like me, you may act lovingly toward them but your facial expression will give you away.
This brings me to the second truth: loving an unlovely is a supernatural act. Love is a fruit of the Spirit so if the Spirit in you doesn't do the loving then it won't get done. Yes, you must be willing, but the real work is done by God through you. Ask Him to help you rearrange your facial expression as well as empower you to be loving.
Third, loving an enemy or a nerves-grater is like forgiveness. It has little to do with their deserving to be loved and everything to do with the love you have received from God. "We love because He first loved us" (1 John 4:19). God is not asking you to concoct love in your heart for them but to pass on the love He placed there.
Finally, if you struggle with hardness in loving the difficult to love, prayer is a great softener. What do you pray? Besides asking God to change their ways, ask for the same you are praying for yourself. I don't understand how it works, but Jesus was sure it would! "Pray for your enemies," He said (Matthew 5:43-48). A closer look at the text implies that something happens to the one praying: a maturing. That's what I love about God! He has benefit installed in even the most difficult of His commands.
There you have it--how to love your enemies. It's a practice none of us embraces, but one that will hug us back when we do.