The necessary information to enable others to help you will of course vary with the problem for which you are seeking help. But here are some minimum guidelines, for users of the #netfilter channel on freenode.net IRC.
First off, it’s always a good idea to put a summary of the problem and goal in your paste. Think of the convenience of the people you are hoping will help you. They are not as deeply involved in your issue as you are. They have jobs and lives and responsibilities of their own, outside of IRC. So start off with this.
For iptables (iptables-legacy) users, you’ll usually need to provide your complete ruleset including packet and byte counters:
iptables-save -c
For nftables users, similarly, you should show your entire ruleset:
nft list ruleset
If the issue involves routing, and believe it or not, most of them do, it would not hurt to include this:
ip addr list ; ip route list ; ip rule list
There are lots of pastebin choices, but I’ll just mention a couple that I know are adequate. My favorite tends to be ix.io, but only if you go to the extra trouble to concatenate all your information into a single paste. I’m not really a fan of pastebin.com, but their “raw” links are good. I really dislike side-scrolling for long lines, text boxes with up/down and left/right scrollbars.
Finally, remember, you’re not entitled to free professional assistance; if you get it, accept it with gratitude. And if you do not, well, that’s too bad, but if you are gracious and dignified, maybe someone will be available and willing to help you later.