Guide to presenting Lemma, Theorems and Definitions

Has anyone ever found a good text which discusses how to present
Lemmas, Theorems and Definitions? I often find it tricky, espically
for longer ones.
Short ones are often OK, for example:

Lemma: For any vector space V, q(V) = 0.

But longer ones can get messy (note, the following isn't correct
maths, just a long Lemma).

Lemma: For any vector spaces V, group G, element g in G, integer x
such that g^x = g then given z is a solution to the equation z=x^3,
V(xz)=g

I'm sure there must be a good general framework for defining all the
bits of Lemmas, but I've found it suprisingly hard to find.

.