Missions and Quests
There are a total of 126 missions in Borderlands, with around 47 of those revolving around the actual plot and your search for the vault.
The other 79 side quests are entirely optional, but they’re crucial for leveling up, so if you skip too many of them you’re going to have a pretty hard time. Aside from the massive XP gains, you can also pretty some pretty helpful items through side quests. They also help you explore Pandora, as there’s a lot of the planet that you never see during the plot missions, as well as some pretty unique characters you wouldn’t otherwise run into.
You’ll get side quests from talking to people, checking bounty boards, and turning in other quests. Like plot missions, some side quests are completed in sequence, where completing one will unlock the next in the quest tree.
Whenever there are new missions available, a Claptrap robot will let you know. To be honest, these constant reminders can get a little annoying, but they do call him Claptrap, after all. Plus, it’s better than the alternative of having to scour the planet in search of quests.
When you accept a mission, it goes into your mission log, which is sorted by area. There’s really no reason not to grab every mission you come across. They don’t expire and there’s no limit to how many you can have in your log at once, so you might as well grab each one as it becomes available.
You can choose one mission at a time to be your active mission and a waypoint will appear on your map to guide you to it. A mission doesn’t have to be your active mission in order for you to complete it, it might just be a little harder to find.
Something pretty important to note is that waypoints don’t always lead you right to your specific objective. For certain missions, such as the ones where you have to collects pieces of weapons, the waypoint will simply point you to the general area where those pieces are located. You’ll have to do the search on your own.
When completing missions in multiplayer, any players who are capable of doing the mission will get credit for it. This means that players who have already completed the mission or who are not yet at that point in the game can help with it, but they won’t receive any sort of reward. It’s always a good idea to let the lowest level player lead the group, so that everyone else can help catch that player up, rather than advancing even further.
There are over 100 challenges to complete in Borderlands that will grant you additional XP. They can be viewed on your mission log page. These challenges vary greatly, from killing human enemies to firing a certain number of bullets. Some challenges will only be met after having put hours and hours into the game. Many challenges you’ll get without ever having actively going after them and they’re a great way to score extra experience.
Article from Gamersyndrome.com