Something about where you are, use your surroundings as inspiration, one thing you have in common is you're both there.
Little fillers can be things like saying you love/hate the song on at the time, commenting on the night, other people etc... It can also act as a distraction from having to speak as you're both still engaged but in listening or watching something else.
Asking if they saw a certain TV programme or film, just things which can strike up further conversation. Ask about their last holiday.
Ask who they came with or are here with.
You can also comment on what they are wearing, more so with the same sex, comment on some clothing or jewellery you like, may lead to a suggestion you could go out shopping together.
Try learning to get a relaxed confidence when out and not engaged in conversation. Relax and smile (just not like a maniac) and try not to look uncomfortable by looking at your feet, fidgetting etc...
Finding something to watch can be good to daydream, whatever works for you - remember, you can be your own best company.