Making someone feel loved can be achieved by the simplest of methods, but they must come
at precisely the right time.
Tell her you love her.
'OK,' you say to your self, 'that's sounds easy enough.'
It is easy, really. But remember to tell her you love her not only while you are being happy together, but when you are being sad together too. Or best of all, when you aren't together, and you have no real reason to be thinking about her.
A phonecall or an SMS or an email out of the blue, saying "I just wanted to tell you that I love you" is one of the simplest ways of making someone feel loved.
Hold her hand in public.
Holding hands can be really important. Not holding hands can make her feel as though you are embarrassed to be seen "with" her, or just as if you don't want to touch her.
Be there for her when she needs you.
This is the big one for me.
Someone who can hold me while I cry, or listen to me when I need to talk about what is hurting me, or just... you know... be there, makes me feel more loved than anything else.
Show an interest in her interests.
Try reading a book she really likes. You might like it, too. Or ask her what her 'special place' is, and if she asks you, go there with her. Or ask to go along to her club or class some time. Or just listen to her talk about them.
But don't pretend to be interested when you are not. Dishonesty sucks.
Which brings me to:
Tell the Truth.
When she can trust you to tell her, when she asks, that you don't like her hair-cut, or you don't like her dress, or you didn't enjoy her book, or that yes, she looks tired, she will know she can trust you to be telling the truth when you tell her that when she smiles it makes your heart ache with happiness.
Tell her she's beautiful
Robert Heinlein said "Always tell her she's beautiful, especially when she isn't" and I agree, but would be glad if he's said "Tell her she's beautiful to you..."
If she knows you see her as beautiful even when she's been digging in the garden, or changing a tyre, or crying her eyes out for an hour (when she knows in her own heart she isn't, in other words) she will feel loved.
I've used "she", "her" and "hers" throughout this, but nothing in this would not apply to a man as well as to a woman.