Do something thoughtful.

They touch you , randomly, in a non sexual way.

Small things like a knowing look from across the room, and the slightest touch with a hand when sitting somewhere together. That is all part of the right chemistry between people. IMO

Doing things you don't like to do; Change the oils in your car,do an inspection under it's hood for signs of; Belts going bad,bulging hoses,low oil,squealing brakes,tires showing cords,alignment when the tires are wearing oddly,simple things most Women do not look for,unless their father showed them how to maintain a vehicle.

Touch. Just being there close. I don't mean sex.

They 'see' you -- the real you -- and aren't put off. They pay attention to what you like physically and emotionally. They listen.

I do have a question, however. Are you saying 'I love you' and not getting it back? Is that why you asked this question? That's another issue altogether. I would want to know why. You shouldn't have to read someone's mind.

I always put the toilet seat down.

#1 attentiveness

When she gets up at 4 and shovels the driveway for me is really the only thing I need to know she loves me.

Eye contact, touch, thoughtfulness, listening.

The look in their eyes of course.

They show up. And they see you.

If he ain't saying it, or asking about it, proceed with extreme caution! Remember ASSumptions lead to terrible things!

When I tell Kate to "beer me" she says "F Y" . I do not ask her to get me a beer as usually we do not have any. There are many things that we do for each other or tell each other that mean a great deal to us and would probably not be understood ny another.

Things like... You mentioned you didn't like coffee so I brought you tea, physical affection/protection (I.e touching waist/ walking on the side of traffic?), Spending quality time, sacrifice

The key is in non-verbal, that is, action(s), many little things done over the course of time which makes you realize that the other person cares for you, loves you.

For me,it was the little deeds such as trying to take care of me when I was not well,(I was a horrible patient as I do not like being fussed over),or,making my favorite food,or tea without a request?

Touching and caring, something as simple as a gentle look.

I'm accessing deep memory here but as I recall something as simple as touch was very reassuring

That depends. Everybody is different in how they want to be loved , or shown that they are loved. Most people don't know what their partner wants and very seldom do they ask.

There are a lot of non-verbal clues but if you really want to know for sure, you're going to have to talk about it.

A hike/bike and observing biology, geography, chemistry and physics and just enjoying while not talking.