What mistakes should I avoid when setting up a UK limited company?

[Balletrist]

I'm preparing to incorporate a new business and I'd like to avoid making beginner mistakes. Are there any common issues with choosing SIC codes, appointing directors, issuing shares, or setting up a registered office? I'm also interested in knowing which tasks should be handled immediately after incorporation. Any practical advice from people who've gone through the process would be really helpful.

[Betsycrant]

Reviving this thread because I just went through setting up a limited company myself. Big mistake I almost made was picking a SIC code that was too broad - it can mess with tax filings later. For shares, keep it simple with ordinary shares
You also really need a separate registered address, not your home. What part are you stuck on most?