What Is The Best Way To Cheer Someone Up?

Try to find some for him just like you.I don't know...

Possible ways to do it is invite him to the beach and let yourself to
be attacked by seagulls. ( Record it and post it on youtube for other
like me to see ) He'll laugh at it, too.

Get a bullhorn and wake him up.
After he gets all fumed and wakes up by the bullhorns, invite him to
some breakfast. That'll  make him laugh and wonder where's your sanity.

Make some time where you both hang out like movie nights or paintball tuesday.
A lot of stupid stuff happens on paintball!

Buy a rabbit. Put it in his
car, pantry, oven (OFF!), or other places he usually goes to. Prank him
next April Fool's Day! Make him be scared of that day! Man, I totally
got off topic, but you know what I mean!

Basically you just make his
day, make him live life, show him he's cared for and all.

It's hard to play both sides of the fence.  No matter how good of a friend you are, they will still feel a loss.   Just be honest with him, but in a gentle way.

I don't really think that he'll see it as cheering him up, Jojo22.  If you broke up with him, just seeing you will probably get his hopes up that you're maybe having second thoughts, and there would be a chance to get back together.  Usually it's just better to let the person work it out alone and try to get over the hurt and loss, and then get on with their lives.  Sometimes it's a good idea to "walk in their shoes" (like if it was you that was dumped (I hate that word, anyway) by someone you really liked) -- you can see that if they came to cheer you up, you would be hopeful that they were coming back to maybe start over?
I wish your buddy to be able to get over this fast, and that you both get on with your lives and do OK.
Moe

Well I will just try to give you my help.Hope that it will give you something.Firstly let him feel that you are always there to help him as a friend.You can use the words like "hi pal" "hi buddy" etc.You can also is the words like "I am always there to help you .its my duty being your best_friend" or "what are friends for.Have fun don't behave shyly.Act natural.Use the word friend or sister as many times as you can but don't let him feel it awkward and strange.When he ask you for help do help him.Act as if nothing has happened as I know it will be strange.Create a relationship like brothers and sisters.Its a beautiful relationship.I hope you'll understand! :)

What I would do  is tell him a funny joke or make him laugh.
Don't make him feel like he is a stranger make him feel like he can be
More than what he really is use fun words like pal,chap,buddy etc.
Make him feel liked or loved don't push him out bring him in and make him feel
confident.