First, welcome to the boards! Second, welcome to D&Ding!
Now, let's get to the meat of your questions.
I'd like to begin by gently pointing out that D&D is not really a "board game", at least, most gamers would cringe at that moniker being applied to D&D. It can sometimes start nerd wars, which are actually kind of funny.
It sounds like you were playing Dungeons and Dragons Fourth Edition. To level up your ranger, you need one of the player's handbooks for this game system. I'd recommend checking out
www.wizards.com, which will have links to the appropriate books. A better route would actually be to go to where you had the session, and ask the people at the store what book you'd need, because they'll have all the relevant info (and might even have free stuff to give you!). The main book used these days is called something like "heroes of the fallen lands" and it has all the rules for your ranger in there.
As for advice to help with the game play? It gets a bit more complex. There's a LOT of advice to give - as with any hobby or deep interest, there's a lot of areas to explore. How much of that you want to explore depends on how much time you want to invest with the hobby. Luckily, you can get by just fine with investing time only as you sit at the table... but you can also spend a lot of free time working on the hobby, too. That's pretty much what this site is all about.
But generally, good play advice? Listen to your Game Master, work well with the other players, don't interrupt when someone else is talking, be a team player, be a good sport, don't cheat or approach the game as if you're there to "win" it, and generally do what you can to make the game "fun" for everyone sitting at the table.
Also, as a ranger, remember it is your job in the group to damage monsters. Not to hold off bad guys, not to try to heal others, and not to try and figure out traps or anything. Do whatever you can to dish out buttloads of damage to dangerous monsters, and you'll do fine.
As for secrets for getting more xp... Well, the game sort of doesn't work like that. Someone giving you all the tricks and ways to maximize XP for individual encounters kind of ruins the game for everyone - it falls under the category of "cheating". And most of the time, it really doesn't matter, especially with the encounters line.
I'd focus less on XP, and more on the team aspect of the game. If you're a happy and fun team player, you'll still probably get the exact same XP reward (maybe even more.... Game masters love handing out bonus XP to people who make the game more enjoyable).
Welcome to the hobby, and hope you enjoy the encounters line!