Yes, I do have some advice.
The only thing I can recommend is to be diligent about writing down the names of the people you meet with and the issues you discuss. You can also advise them to register if they do satisfy the 20% rule. I don't think, though, that it's up to you to make sure they satisfy the rule. You already have enough on your plate.
However, if you do have doubts, I suggest that you contact our office. We keep a close eye on what goes on in the news. We try to be proactive. If anything shows up on our radar, we contact lobbyists. We endeavour to check the information and make clear what their obligations are. If you have any doubts, let us know. We can't know the name of every single company or organization you meet with.
The only piece of advice I can give you is to write everything down, because I could ask you to confirm the information I was given. If any information needed to be corrected, you would have to tell me that. I could also ask you to confirm whether you had indeed met with certain people.