I teach English to adults in England and use the following website which has lots of materials on it for teaching English:
UK Adult Basic Skills Resource Centre for students and tutors. Home Page
I have to follow a curriculum (because of government funding!) in England & it sounds like you should look at the Pre-Entry / Entry 1 ESOL stuff to begin.
There are so many websites out there, just put "teaching English" in to a search engine & you'll have a ball!
I think if you start with greetings, introductions, saying goodbye that's always a good start... If they need vocab for work you could get items or pictures and give them the words and phrases they'll need to use at work.
Directions, talking about themselves & families, are always good topics because they're familier subjects. Spelling using the alphabet is a good idea as they may have a different alphabet in their country - pronunciation practice is always good too.