Learn a few important words because when you know them you can explain many things, even without grammar. Listen to how much people can say when they need to: notice the ways that work, so that even without a translator, you can get some information across.  

For instance:

• Numbers 1-10.  You can also show these numbers with your fingers
• Basics: please, thank you, Hello, How are you, I'm fine. 
• Simple verbs, as 'orders': in spoken language this is most common: Come, go, look, wait, stop (many of these can be shown with hand signals). Like, have, am are less easy to show with signs.  See First Verbs
• Key adjectives: sorry, tired, hungry, angry, ill, happy, OK, see First Adjectives
• Question words: who, what, where, when, why
  
• Simple sentences: grammarless, but understandable
  
  • No understand (I don't understand).  A blank look also works.
  • Again...  (Please say it again)
  • I want water/ key/ internet (need has a stronger meaning than want, but for basic communication, they similar).  The opposite?  I no want....