what to do with inventory

Well, the first item I will deal with is loot.  Sell most items would be my first response, generally speaking most items can be sold for money.  I usually go back to base, check all my companions items to get the best on them, keep a few on hand and sell most of the rest.  A good bit of the stuff you get in game is simply trash loot for money, at times it looks like a weapon or armor, but it is below what all your guys have so it is trash to be sold.  If it is rare, unique then that is different, but most can be sold.  I know you get a chest later in the game that allows you to store almost unlimited stuff in it, and I find I put stuff there and never go back for it.... IIRC I also think you can upgrade your inventory later in the game to hold more stuff, but if you are selling stuff like you should it really shouldn't be an issue.  You usually also get a merchant in most areas after you complete a quest or two sometimes but they are there to be used.

As far as a game guide, well there is the Wiki online, as well as many walk throughs.  But I have to say for me, half the fun of the game is wandering around and finding all the stuff out on my own.  This game shouldn't really be played as a go here do this, go there do that point A to point B to point C type of game.  It should be some of that, but mostly wander around find what you need complete the quests as you find them and have fun.