The weather is a great conversation opener since it affects everyone.

You can talk about the heat, cold, wind, rain, cloud, snow...

For the later part of the week, you can ask people about their weekend plans.

For the first part of the week, you can ask people about how their weekend went.

There is an almost limitless number of news and current events that one can bring up

Conversing about news and current events allows you to get into deeper conversation since you can get information on their personal views.

There are countless things that you can talk about related to your surroundings. You can talk about the music playing in the background, the dinner menu, history of the area, the drink they ordered, the decor, a painting on the wall, the score of a sporting event on TV...