Okay, firstly Ho-Oh is not only Fire, but it's Flying. This means that Ground-type moves are ineffective on Ho-Oh, so don't worry about Ground-types.
I'm not one of those people who do EVs and stuff, I'm all about fainting the damn Pokemon under no circumstances. xD
But I'll suggest a few moves:
AncientPower - Non-Physical
AncientPower is a rather weak physical move, but it may also rage the Pokemon's stats at once, so when it does that, it's incredibly useful. Otherwise, though, it's a really bad move, and I wouldn't recommend learning it at all really. :/
SolarBeam - Physical (TM)
Well, there's not much to say about this. SolarBeam is just plain awesome - but it continues onto the next turn, so if you're playing competitive I wouldn't recommend it. But if you're not, this is good against Rock-type Pokemon. You'll want to get rid of them ASAP, and SolarBeam does the trick. But remember, don't learn if you're playing competitive. Otherwise, get that TM and learn it. NOW. o_o
Roost - Non-Physical
Consider learning this move, it's not half bad - I mean, it's nice to have when you need it. It heals 50% of your absent HP, so it's good when you are at 1HP. Works just like a Revive, really.
Overheat - Physical (TM)
I know Ho-Oh already has some major Sp. Atk, so consider this move as well. Overheat can do some pretty damn good damage, despite the loss of all that Special Attack. But like I said, I don't care about those stat thingys. xD So, if you are like me, go for it. :P
I'm not suggesting that has a full move set - I mean, these are just some suggestions.
Oh well, hope I helped. :)