He wrote The Five Love Languages in which he divides these ways into the following categories:
Words of Affirmation
This is when you say how nice your partner looks, or how great they cook, or what an amazing person they are. It's all about building up your partner, making them feel good and reassured.
Acts of Service
If you or your partner show love by doing things for each other, then you fall into this category, however its an easy trap to fall into if you do these acts begrudgingly.
Things like helping around the house, hanging the washing, going to the market, or putting the kids to bed need to be done with joy in order to be perceived as a gift of love, Chapman says
Quality Time
Some people place spending time together as the most important way to show love.
Not so much just sitting there on your phones, it's about connecting while doing something, even if you are just chilling.
Receiving Gifts
Giving or getting a gift from your partner can be the best way you may express love, or like to receive it. It doesn't need to be expensive or flashy, it's more a way of showing you care or are thinking of each other.
Physical Touch
If you always like to be physically affectionate, and not just sex, hugs, kisses, back rubs etc then this is likely where you fit. This physical contact is very reassuring and meaningful to someone with this love language.
So now you know the categories, figuring where you fit is easy.
As marriage.about.com says, ask yourself:
How do I express love to others?
What do I complain about the most?
What do I request most often?
Get your partner to do the same, it could be that you are in different categories, but as Chapman cautions in his book, "We're not talking comfort. We're talking love. Love is something we do for someone else. So often couples love one another but they aren't connecting. They are sincere, but sincerity isn't enough."
So you need to get out of that comfort zone to meet each other's emotional needs, while people tend to naturally give love in the way that they prefer to receive love, there needs to be a middle ground.
So once you have figure out each other's love languages, it's time to communicate in them.
If your partner needs words of affirmation, surprise them with some sweet messages through the day on why you love them.
If it's quality time they need, despite your busy lives, commit to a date every week where you hang out together, and leave the phones at home.
If your love loves physical touch then get some nice massage oils and surprise them with a massage at the end of their busy day.
If gifts are the way to your lover's heart, then you don't need to blow the budget, it's about the thought.
Also, when it comes to birthdays or Christmas, make sure you put effort in, even if its organising a nice dinner.
If they like things done for them, use your initiative, be equals in the household, you can mop the floor, cook dinner or even asking how you can help will go a long way.