1. Check and recheck your orders
2. Always keep some railway capacity spare (remember units moving from previous turn will continue to consume railway points)
3. Always remember to rebuild railway destroyed by AI or Enemy player
4. As CP, you either use your navy in 1914 or do not use it ever. You can use it against Russia of-course, but unless Entente blunders and sends a piecemeal battlecruiser fleet or something, do not attack them after 1915.
5. VP is not important, NM is. Ignore VP.
6. Try to be as aggressive as possible in 1914 and take those VP/NM points in 1914. Even if you lose 300k men doing it, that NM will help in the long war ahead.
7. Build cheapest units first, only "luxury units" you should build in 1914/early 1915 is Fighter aircraft, otherwise only Infantry and Artillery.
8. From 1916 you have no manpower, so build hospital units, engineers, pontooners, pioneers etc, these are force multipliers for existing largest armies.
9. Get best generals commanding the largest armies and ensure GHQ is near (within 4 paces) of the attacking armies.
10. Thumb rule - Use English (including Anzac and Canadian), German troops to attack, rest ideally shouldn't.