When it comes to introducing the protagonist, here's what
Dan Harmon has to say about it:
1. "You." - ESTABLISH A PROTAGONIST
The audience is floating freely, like a ghost, until you give them a place to land.
This free floating effect can be exploited for a while - closing in on the planet Earth; panning across a dirty shed. Who are we going to be? But sooner or later, we need to be someone, because if we are not inside a character, then we are not inside the story.
How do you put the audience into a character? Easy. Show one. You'd have to go out of your way to keep the audience from imprinting on them. It could be a raccoon, a homeless man or the President. Just fade in on them and we are them until we have a better choice.
If there are choices, the audience picks someone to whom they relate. When in doubt, they follow their pity. Fade in on a raccoon being chased by a bear, we are the raccoon. Fade in on a room full of ambassadors. The President walks in and trips on the carpet. We are the President. When you feel sorry for someone, you're using the same part of your brain you use to identify with them.
Lots of modern stories bounce us from character to character in the beginning until we finally settle in some comfortable shoes. The bouncing can be effective, but if it's going on for more than 25% of your total story, you're going to lose the audience. Like anything adhesive, our sense of identity weakens a little every time it's switched or tested. The longer it's been stuck on something, the more jarring it's going to be to yank it away and stick it on someone else.
I wouldn't f*ck around if I were you. The easiest thing to do is fade in on a character that always does what the audience would do. He can be an assassin, he can be a raccoon, he can be a parasite living in the racoon's liver, but have him do what the audience might do if they were in the same situation. In Die Hard, we fade in on John McClaine, a passenger on an airplane who doesn't like to fly.
If you've already established a protagonist and want to make him likeable somewhere further along in the story, then my advice would be to keep him from doing something unethical or mean to innocent characters. Don't let him belittle people and act like an all-around horse's ass.
I recently read
Catcher in the Rye for the first time, and the main character, Holden Caulfield, is a spoiled snot who constantly finds fault with everyone else. I kept hoping for him to get beaten to a pulp, but it sadly didn't happen. Terrible character. This is a good book from which to learn what not to do as an author who wants to write a likeable protagonist.
On the flip side, a hero who sees the value in everyone and is willing to make sacrifices for the benefit of others will earn reader sympathy. If the hero is heading for his car in the parking lot, and he happens to see an old woman struggling to get her groceries in the back of her car, then have him take a moment to help her out. Simple things like that can help take the edge off an otherwise cranky private detective (for example).
Anyway, just my thoughts. Hope that helps.

Make sure they're not politicians, lawyers, or members of House Lannister.
