Infernape should always go mixed to some extent since that's his greatest strength. Which end of the spectrum you focus on is up to you:
Infernape @ Life Orb/Focus Sash
Blaze
Hasty/Naive
- Fire Blast
- Grass Knot
- Nasty Plot/Vacuum Wave
- Close Combat
The traditional mixed Infernape leans towards Special mostly, and your EVs generally should be built around its Sp.Attack and Speed mostly, with a few in Attack to boost the power of Close Combat a bit. Nasty Plot makes this set very difficult to wall, since most special walls won't like taking Close Combat attacks and everything else will struggle to hold off Nasty Plotted Fire Blasts from this thing. Vacuum Wave can be used instead if Infernape's frailty puts you off of using a setup move, and if you'd like a good revenge-kill option to take out faster foes.
Or:
Infernape @ Life Orb/Focus Sash
Blaze
Hasty/Naive
- Close Combat
- Stone Edge
- Swords Dance/Mach Punch/U-Turn
- Overheat
Same premise as the previous set except focusing on physical attacks as opposed to special attacks. Close Combat will be the attacking move of choice here, alongside Stone Edge to pick off Flying-types. Overheat will cripple the vast majority of physical walls that will come in on you, possibly OHKO'ing some of them, and the third move, once again, is personal preference.
Naturally, there's also the mid-way moveset between these two that simply combines Close Combat and Stone Edge from the physical set with Fire Blast and Grass Knot from the special set, although Infernape risks spreading itself a bit thin here - it's certainly a viable option though, so take your pick.