Diplomacy research is the only way, and dont attack them, turn off auto attack until actual war. Once you can give money and metal/crystal, and have envoy bonuses, you should get a cease fire option pretty quick. We never usually bother with that to much. If he dont attack you he is an ally in the making.
The guy that attacks scouts and envoys, and just wants to blast everything that moves usually dont last long. Send a scout both ways, the side that tries to kill your scout is meat, the other side tries to kill your scout or envoy as well, best get your game face on a do some beggin' for a partner. Usually one or both sides will let scouts pass and envoys park. Start colonizing towards the sun and not deep into your neighbors territory. Get 3 or 4 planets and someone will be blasting everything or going deep in a friendly or your territory. Team up and go kill 'em.
Get near is HW and he may give up, tell him he has to feed you and no military ships for a while, or if he has an ally, make him take his fleet to his allies well and declare war on him to prove allegiance. Ahhh, good times. Making someone your bitch is the best; I rather go down in flames, some stick it out.
If you have a good group, FFAs blow set team games out of the water.
Oh, BTW, dont let your ally build starbases in your well without permission, chances are they are preparing to backstab you.
Trust me, I invented it and paid the price many games after.