Most people will prefer one or more of the above over the others. My wife values touch and words. Simply putting my hand on her thigh, letting her know that I'm there and thinking about her, helps keep her "love-tank" full.
I try to tell her how I feel often. There's a lot that goes on in my head and it doesn't always make its way out of my mouth. I often think fondly about her but never speak it out loud. I'm getting better at vocalizing my appreciation and affection, rather than just assuming since she "knows" then she shouldn't need to hear it again. In other words, I'm not saying "I love you" because I think that she's forgotten or doesn't believe that I do, I say it because it's just a nice thing to hear. It means, "I'm thinking of you; I appreciate you; I'm happy being with you; I enjoy you; You're special to me; etc."
Show someone you love them by planning something. It doesn't really matter what, but plan something that incorporates things they value. It makes someone feel special and noticed when you've considered the things they like, and have spent time to set something up for them. Listen to what they say in conversations and take action on things they mention wanting to do. Combine their desires into an event/trip. Take care in your planning to make sure that everything is taken care of so they don't have to worry about anything. Things as simple as making sure the gas tank is full before you leave for a trip can create a great deal of comfort for your friend. Be attentive to their needs and make sure that you've considered them in each step along the way.