It simply happens. And it's not that big of a deal.
- When somebody loses their job share your condolences and all that, but make sure that you send them some cheer! Usually losing a job opens you up for a better opportunity. Make sure that you share that with them!
- Ask them out for coffee, sometimes people don't know what to do with themselves and something as regular as coffee helps them realize that their job, NOT their life has been eliminated.
- Make sure that you ask them for their non-work affiliated contact information. This is part kindness, part shrewd. I'm all about maintaining communication and alliances. Your "business friend" will have to eventually work somewhere and probably in the same industry, keeping up with them is to your advantage. You also may have information about another position or consultative work for them in the future.
- Do NOT ask what happened and why they are not there anymore-they probably do NOT want to talk about it, but if they do want to talk listen without prejudice.
- Do NOT gossip about your conversations or chat with anybody else about them even if asked.
If you have unfinished business with the company that your colleague has been fired/laid off from, contact the other company but never speak ill of the fired colleague and in turn never participate in negative conversation about the person who has been let go or the situation surrounding the reason, it is none of your business.