How to make sure a proof is correct

Leslie Lamport's paper on "How to Write a Proof" (PDF) offers some useful advice.

Lamport suggests structuring the proof formally, with each statement accompanied by its own sub-proof in terms of simpler claims. How far should one continue this refinement? Lamport says: "My own rule of thumb is to expand the proof until the lowest level statements are obvious, and then continue for one more level. This takes discipline."

Go through all the steps of the proof and check them!

This is the only way I know

What Topology does a Straight Line in the Plane Inherit as a Subspace of $\mathbb{R_l} \times \mathbb{R}$ and of $\mathbb{R_l} \times \mathbb{R_l}$

Compute $\lim\limits_{n\to\infty} \left(1+\frac{1}{n}\right)\left(1+\frac{2}{n}\right)^{{1}/{2}}\cdots\left(1+\frac{n}{n}\right)^{{1}/{n}}$

Prime spectrum of a ring, understanding geometry

Why $\sigma$-algebras represent information, and what information does $\sigma(X)$ represent?

How does one show a set of axioms is independent? (of each other?)

Prove that Every Vector Space Has a Basis

How to Read a Varnish Histogram?

Is cURL standard part of all Unix-like operating systems?

Ubuntu 12.04 LDAP SSL self-signed cert not accepted

Debian - "WARNING: untrusted versions of the following packages will be installed!"