A note to easy alliance, or rather, things to keep in mind to help build good elationships:
1) Anytime you buy or sell things from/to an empire, you get positive points with them (You can only buy things when you have 25+ relationship)
2) If the empire has any planets under T3 (except Grox), improving the T-Score will gain a large amount of points.
Note: All Empires start with a T3 planet, and usually (9 times out of 10) only have system when you meet them. Some empires will have 2 planets in a system, but this is uncommon.
3) Most people can get by with embassies (costs money and require a very tedious badge that requires you to talk to 100 different empires) or the happiness ray
(which requires a considerable amount of energy).