Before flashing a ROM you must flash ClockWorkMod recovery. Once you installed CWM you must boot in recovery and then do the followings step:
1) wipe data/cache
2) advanced -> wipe dalvik cache
3) install zip from SD card
4) choose the zip and confirm
For the most stable cm10.1 I suggest you Cm10.1 by Maclaw or the last CM10.1 by androidarmv6 team.
My favourite is the second one !
These are pure CyanogenMod ROMs with no moddings. I don't like modded ROMs.
Sent from my GT-S5830 using xda app-developers app
Device: Samsung Galaxy Ace S5830
Rom: CM10.1.6 by Androidarmv6 Team
Kernel: MA6 Kernel by Mardon