I see story telling like fishing;
Hook the audience - This means making your story relevant and interesting to the audience, or if it is not interesting making it interesting (relevance, exaggeration, enthusiasm etc).
Start reeling - Common mistake, you have their attention they are listening you go off on a tangent and loose them or go back to the dull way you would usually tell stories.
Add elements to the story which will compel them to hear you out ("then the weird guy, actually I'll get to him later", "So I am sat there with this massive fucking box no idea what is in it" etc).
Also you need to be gauging the group, if one person looks bored draw them back in ("I am sure you know the type of person I am talking about", "I mean what do you think about that" etc).
Almost in the bag - This is when you can elaborate, get ridiculous with you gestures and enthusiasm. Ideally you will have been building them from a good level to an insane level and keeping the audience at the same level (like being on a ski lift, then the end part of the story is bombing it down the side of the mountain).
In this stage you want to tie up a few of the loose ends but save the real who-dunnit part till the last stage
In the bag - This stage is tying up loose ends, sprinkling some humor and releasing the energy you have built up in the set, so the story and telling of it seem like events in their own right.
Hope that helps
also, looking at someone that you find interesting and modeling yourself on them can be handy. For me it is pure Russell Brand his gestures are amazing.