(1) Get the highest level armor you can. For a ranger, that would be an armor class of 70. While you are learning the game, you may want to only add minor runes to your armor. They help make your skills more effective, but won't impact your health. Get the highest vigor rune you can afford. Major vigor is not too expensive, but the extra health can help in the early going.

(2) Know your enemy. Use the wikis to learn about the explorable areas, missions, quests and enemies before you head out.

(3) Make sure to use good skills and set up your attributes to effectively utilize those skills. PvX Wiki has lots of good build templates which you can use as a starting point. Setting up your heros' skills is also very important, as the base skill sets the heros have are rather sad.

(4) For a ranger, you may want to take advantage of having a pet along to stay alive. Your pet will need to level up, but once they hit L20, they have max level armor and can help keep the enemies at a distance. I have also seen multiple people early in the game run with "pet packs" (having a pet on their character and all their heros). While not optimal for all areas, it can help even the odds a bit.

(5) Have a necro MM hero and/or Spirit Spammer hero in your party. MMs are very VERY useful in many areas in the game. They help create a barrier between the enemy and your party, helping you survive the battles. Although not as easy to obtain, a Rit spirit spamming hero can also help tremendously, especially in areas where there are no corpses for a MM to utilize. Decent hero MM and spirit spammer hero builds can be found on PvX Wiki.

(6) When possible, pull enemy mobs to your party. Pulling (aka "luring") is a simple concept, but can take time to master. Not only does pulling get the enemy to come to you (away from some defenses, such as traps, they may have in place), but most importantly it helps you only aggro one mob at a time. Rangers are great pullers for normal PvE play. Using Troll Ungent + Whirling Defense just before you pull will help reduce the possibility of getting killed in the process. Look for tips on pulling on the Wikis.

(7) Get in a guild with people who can help you. Most of the best players in the game didn't get that way by themselves, they ventured with others, asked questions, and learned from their experiences.