I realise that in most, if not all, unpressurised GA aircraft there will not be supplemental O2 available, however not one poster, including those citing commercial passenger aircraft, has mentioned donning an Oxygen mask. First action when O2 is available is to get on 100% oxy. Smoke not only upsets your eyes.
Ha Ha, nice one old fella. The wannabes are so keen to tell you what aircraft they fly they often forget the basics!
The second action after getting the mask on is to refer to the abnormal/emergency checklist, if you can still see it! The strange anomaly about amateur pilots is they try to use checklists when you dont really need them but never consider them when you really do need them. You could argue for ever what is the first action you should make but the most important action is in fact the last action-fly the aircraft to the safest place!