Is this Against Adsense TOS to encourage someone or to tell someone to signup for my adsense referral programme?
No, it isn't. You can't encourage people to click on PPC ads, but you can do it for PPA programs. If you are unsure - ask adsense team directly.
You can tell your friends to sign up verbally, but if you spam saying that signup for adsense from my website, you might be in trouble.
I think you could do this but only in certian ways you cant just have a normal site a adsense reffal and say yo everyone click this! you have to do a blog all about making money via adsense and talk about it.
Which referrals? If it's referral's 2.0 then you can ask people to click on them (such as products), however if it's a referral to join adsense or download firefox then I don't believe so.
No it's not against TOS. Actively endorse the products you refer. Unlike with AdSense for content ads, we encourage you to endorse referral products by calling attention to the button or text link. If you believe in the quality of the product that you're referring, feel free to let your users know! Of course, in line with our policies, you may not click your own ads nor encourage conversions for deceitful reasons. Source Hope this helps
Well in my opinion in referrals you could advice or encourage as payment is made after signup i.e. conversion ........... however still it is better to dig in adsense forum