Purity: removal of hadath and disqualifying najasah, with limited concessions for genuine inability.
Covering: required parts must be concealed; in complete lack of clothing, sitting with gestures is preferable, while standing also suffices.
Intention: inward specification of the prayer; the Hanafi view accepts intention formed before takbir where no separating act occurs.
Qiblah: face it when known and possible; in serious fear, ability governs, and uncertainty calls for inquiry and ijtihad.