i always contact them via, pm or email. I have an email template that i use to contact webmasters. it's proven to work for me. I never put there link up before i contact them. i tried that before but found myself doing twice the work looking to see if they responded and if they put my link up. once i get a positive response, then i put there link up even if they haven't put my link on their site yet. then i follow up.