The Right Way And The Wrong Way

Just because it's someone's job to help you doesn't mean you need to be rude to them. Why not just say,

"Excuse me, could I get..."

"Excuse me, could you show me..."

"Excuse me, could you help me to..."

Shit, you don't even need to excuse yourself, but at least say what you need help with. Don't just go up and stare, waiting for the person to acknowledge you. Chances are they are busy with something, and don't care too much about people not in need of their help. Which is how you are acting.

To stand silently over someone in this way is rude. Ask for their help, and chances are it will be cheerfully provided.