you can mix berries through the shake to give it a better flavour. Berries like strawberries, raspberries and things like that. You can also add a teaspoonful of coffee if you want a coffee flavored shake. Here in Australia most doctors recommend a specific brand and mine was Optifast. Not sure if you have that brand in the US, but if you talk to your pharmacist, he will be able to guide you.
Please excuse the grammar - I am trying to think of all the American words that you call the things. As an example, we call diapers - nappies. When I visited Disneyland in LA, I needed to buy some disposable ones because I had used the last one in the bag. I had said on the plane all the way to the US - diapers, diapers, diapers... and when I actually had to ask for them - do you think I could remember what you guys called them - NO WAY. It took half an hour solid of interpretation to explain what I was asking for. Pity I didn't have my daughter with me at the time, because I could have just lifted up her dress and pointed. I had left her with my mum. So with pharmacist, we call them chemists... but I am not sure what you call the people who work in your drug stores... I will leave the interpretation to you :-)