Check with your own solicitor/lawyer that the land actually belongs to the builder/developer, as I have experience of asking the builder for a Certidao de Registo Predia, he couldn’t produce one to prove he owned the land he was building on.
Check that plans have been approved; sometimes they may have to be adjusted by the developer if the plans do not meet the regulations, make sure you know exactly what has to be reduced on the property you are buying. If you are having plans changed then make sure they will get approval.
If the plans have been adjusted, ask for a revised contract to be drawn up. Make sure you get this checked over, as you would have done, with the initial contract before you sign.
If it is a small project of a number of apartments in one block and it has a flat communal roof, make sure it says 'communal' on all official documents that you are provided by the seller, clarify that this is on the documents/plans with your Lawyer, as all official documents have to be written in Portuguese but you can have a copy translated into English before you sign anything.
There may be some issues with the person selling land/property who may not be the legal owner of the land, so you must get this checked out.
Make sure plans have the words CAMARA MUNICIPAL stamped on each paper which shows the plans have been approved. Or ask for the official letter saying Aprovacao.
What you need to ask for:
1. Certidao de registo predia (to prove ownership of land)
2. Copy of the contract (to show your lawyer/solicitor)
3. Stage payment details
4. Completions date
5. Service charges per month
There may also be other things to consider that your solicitor/lawyer will make you aware of. I was informed that some developers may offer you a discount if you pay the 10% (or other %) deposit. I don't know how true this is!