a) Japan adopts their modified semi-auto Pedersen rifle in 1936, Germany clones the SVT-40 for themselves.
b) Closer tech exchange between Italy (P.108 & P.133 et al), Germany, and Japan, ideally with development of the Me 261 in quantity before the war.
c) Keep von Ohain's original jet research team together at Heinkel and coordinate with Jumo and BMW for R&D. Let him pursue the HeS 30, perhaps the HeS 10 and HeS 4p as well.
d) Stick to original plans and timetables for both syntheric fuel plants and overall wartime factory production.
e) Hit the British Home Chain earlier and avoid targetting the civilian populations
f) Eisenhammer is a go from day one of Barbarossa, even if it means one-way missions for some crews.
g) No Pearl Harbor under any circumstances!
h) Germany needs a long-range bomber whether by trade (P.133, G5N, etc.), development (Me 264, He 277, Fw 300) or 'acquisition' (MB 162, F222, Czech or Polish model, etc.)
h) Coordinate production for submarines and aircraft using modular assembly system from late 1930s and toss the Walther system out in favor of larger conventional submarines (Type XXIs in the water in late '43 or early '44, maybe another model makes production before war's end)
i) Germans and Japanese to coordinate all research via in-house government offices (no '3 dozen groups all working on an aircraft fuse')
j) Greater scepticism about crypto security by all 3 Axis powers from day 1
k) Keep Italy successful in Greece from the beginning to let Germany hit Russia in early May instead of late June