USD is the de-facto currency and only recent USD notes. You get a Visa upon arrival at the airport. Pay in USD cash only.
No standard plugs. If you are staying in a hotel, they have adaptors available for the common types of plug.
Communication network there is very poor. Basic internet only. Check with your telco if any roaming available there. You may need to bring along a simple phone, and buy a pre-paid card when there to contact friends as land lines are few.
Bring along your driver's license as you may need to drive while there. It is right hand drive in ET. If going off-road on 4WD, take the full insurance package. The roads there are treacherous, bad condition and unlit at night once out of Dili.
Having said this, there is a Singapore owned restaurant by the sea, near the Jesus statue. Good fresh seafood and cheap too!