Selecting a sliding patio door
Double-glazed (toughened safety glass) without question.
Possibly tented glass (would help a little on those intense summer days).
uPVC frame (and uPVC trim pieces). uPVC doesn't seem that popular here in the USA (at least here in the St Louis area), but in the UK it is extremely popular (mainly due to its almost zero maintenance requirements).
Built in anti-lift device/mechanism.
Good quality hardware &amp; locks.