How would I give just a simple shape many many more faces and vertices to have a nicer overal piece?

Um. Well I am attempting to model a really detailed war axe, or the likes. Wanted to get the basic shape of it and then, add the detail and customize from there. Any advice?

Im pretty new to modeling, but i found that good textures can work towards 90%of your detail.
Make an outline of the axe,and make a bevel on both sides. the basic shape shouldnt be too many sides. I, personally, would spline model it using only corners (no bezier curves). have about 5 segments. for the rounded side of the battle axe. you can make it smooth enough with 5 sides. The stick should have 6 sides to simulate a rounded objecs, and only 2 faces per sides. Then, put some detail where the stick meets the blade to match how you want it to look.

Now, when you texturethe stick, turn on smoothing so it'll render round. for the blade, just use a really good texture and make a realistic bump map.
that should be around 100 - 150 faces, and still look pretty good.

Seriously play with textures and Bump mapping. Ive found that you can make some very realistic detail with low recourse needs.

Adding polygonal detail is done the same way you model the rest of the axe... you add more polygons and position them how you want them.

You can either subdivide/meshsmooth the whole model or the areas you want to add more detail to, although both methods are quite 'dirty' approaches.
Ideally you will add the polygons you want with a knife tool or whatever your 3D app offers to cut/add edges to polygons. This will keep a mesh clean that's much easier to work with, be it for further modeling, UVmapping/texturing or whatever.