As soon as you've completed a small piece of coding, no more than a couple of hours work, review all the new code with a colleague. There won't be too much code, so it won't take too long. Invariably, the colleague will have suggestions for refactoring or tightening up the code which you should implement straight away.
This can be a good second best to PairProgramming for straightforward coding tasks. And if PairProgramming is seen as a bit way out and freaky, nobody can argue that CodeReviews aren't very solid, respectable and a GoodThing.
This is one of a number of SoloProgrammingXpWorkarounds.
(See ExtremeProgrammingCodeReviews for "mainstream" XP CodeReviews.)
Having only one other person in a code review, as in pair programming, is effective, especially in an environment that promotes ongoing reading and refactoring of code.