I like my coffee more fru-fru & this method lets you mix without curdle of the protein...
1/2 scoop protein powder (use inspire which has 30 in a full scoop, so one cup 15g+ & enjoy cinnamon, caramel or chocolate flavors but you can use no flavor if that is your preference)
1 tbsp sf creamer (your flavor choice) -refrigerator cold
1/8 cup non-fat milk - refrigerator cold
sweetener if you like ( I use splenda)
stir the protein powder with the creamer in your cup until its thick an smooth, add other ingredients if you want them & stir again until smooth then mix in coffee (it can be as hot as just brewed)...The trick for this smooth coffee is that everything is mixed cold before adding the coffee, if you still want it hotter after you have added the coffee it is ok to micro for about 20 secs with no ill after affects
Another way when I need portable for travel is to add the liquid protein drink Oh Yeah, it is also in a number of flavors so you have to want flavor coffee that is more like a latte for this to taste good...They have vanilla, choc, cookies-n-cream (like this one

)...Just add to your coffee like milk, as much as you like, more will equal greater cafe au lait taste...