For stronger drinks from your bartender, look at the pour while he's pouring it. For even stronger pours give him a cognitive load while he's pouring, especially starting during the pour, such as "so what's the best food on your menu?"

Giving someone a cognitive load is amazing, it's basically an easy way to get them to continue doing what they're doing a little longer.edit: obviously this refers to liquor pours, not drinks like beers where it goes to the very top no matter what