Another Way of Doing a Toast: "Otsukare (-sama)"

As everyone knows and some other senpais comment, it's usually the case with a toast that we say "Kanpai" ( as you say "cheers") before we begin to drink at a party. But we have another way of doing a toast.

In a casual setting where we go out for a drink after work before going home, we sometimes say together "Otsukare-sama" or more simply/casually "Otsukare" instead when we begin to drink at a drinking get-together (that we call "nomi-kai." We Japanese people often go out for a drink (a.k.a. "nommunication") after work, not only with their friends, but also with their colleagues, bosses, and subordinates, clients, and business partners.

"Kanpai" (a general expression) is also OK even in this situation above, but "Otsukare (-sama)" (a phrase that literally means "You must/may be tired") tends to be used in an informal situation when we go out drinking with our friends or friendly colleagues/bosses/subordinates after work or some project (that may "tire" us), while "Kanpai" tends to be used in a formal situation when we drink with our clients and business partners, or in a celebratory situation (for example, a birthday dinner/party). When "Otsukare (-sama)" is used, there is usually no speech before we do a toast with this phrase as it tends to be used in an informal setting.

FYI, we often say Otsukare (-sama)(-desu or -deshita) to someone also as a greeting when he/she has finished his/her work for the day, and when he/she is leaving his/her office for the day. We use this phrase when we feel like thanking/rewarding someone for his/her hard work and good job.
http://japanese.stackexchange.com/questions/1158/when-is-it-appropriate-to-use-%E3%81%8A%E7%96%B2%E3%82%8C%E6%A7%98-otsukaresama