Firstly, Poland should have solidified it's borders.
Easier said than done. Poland just didn't have the money - and they had a long, long border with hostile neighbours. Virtually none of her neighbours at the time were on good terms with the Poles, except possibly the Czechoslovaks - so Poland would have had to defend a very, very long border. It just wouldn't have been possible to solidify them, especially given the economic circumstances of 1922.
Secondly, maintained a large Reserve army (ala Switzerland)
This might have made sense, but only if the combat plans were to involve guerilla warfare rather than the conventional man-to-man battles of the day.
They could have used the WWI planes in 1939 not as fighter planes but as ground support much like modern day helicopters.
It wouldn't have done anything to prevent the rapid German advance - WW1 aircraft would have been absolutely useless against blitzkrieg.
Fourth, manufactured as many armaments as possible (i.e., small arms, artillery, ammunition, etc. don't import).
But with what? The financial troubles of the 2nd Republic are very well known.
Instead Poland tried to compete with Germany, as a result they never had enough stuff.
They were numerically outnumbered and psychologically beaten by the realisation that they had to fight Germany alone - sure, they might have lasted a few more days, but in your scenario, the Germans would still have managed to succeed. It also wouldn't have helped a bit against the two pronged attack.
I've said it a thousand times - the only hope for Poland in 1939 would have been to fight a guerilla war where potentially, every man, woman or child could be carrying a gun in which to murder Germans with. The Russians wouldn't have wanted to invade as long as the Polish armed forces were intact - and the Germans may not have had the stomach for a long guerilla war that they couldn't win.
But really, Poland lost the war in the early 20's - by conquering part of Lithuania and refusing to grant autonomy to Galicia - they all but sealed their fate. A smarter move would have been to build alliances with Czechoslovakia and Lithuania, as well as granting Ukrainians a great deal of autonomy in exchange for military cooperation. If they had also enfranchised the Jewish population, then - perhaps she would have survived relatively intact.