I usually just use one at the end if appropriate as a brief way of expressing the "tone" of my message or what facial expression I would make.
This

one I limit mostly to irony, it's commonly overused by insecure people. Used sparingly it can can clarify that a message isn't intended to be negative, when it could very easily be interpreted like that without the emoji.
Using just a ton of emojis can be appropriate if you have developed that type of rapport or it's a sort of inside joke or something. Don't do it by default though.
I use "haha" a lot more than I use "lol". The length of the "hahahaha" says something about just how funny I found it to be. "Lol" is outdated and people who say it typically don't laugh in reality, it feels like the laziest way to express something to be slightly amusing, not really funny.