Important Note: Make sure to use Neogeo zipped rom sets from a recent MAME set like 0.144 and higher. Do not use sets from Neorage or FBA since they are not 100% compatible. Also do not unzip or rename any game files.
Create a game directory on your device (named Neogeo for example), using a file manager app or your PC
Obtain neogeo.zip from a recent version of MAME and place it in the directory. If you're having trouble finding the right one, search Google for "MAME Bios"
Obtain at least one game zip and place it in the directory, making sure it's on the compatibility list below. For example, if you want "Metal Slug", you'll need the file mslug.zip
Launch NEO.emu and select "Load Game", then navigate to the directory you previously made and select the game zip you want to run
Once you've navigated to the game directory, you may also select "Load Game From List" to show the full titles for easier game selection
Emulate Timer: Enable the per-scanline timer used in some games for raster effects. "Auto" enables it using a built-in list of games that require it (mostly soccer ones). Turn it off if you experience flickering graphics.
Make/Use Cache Files: Create and use .gno cache files when loading a game. These files speed up loading and reduce memory usage of games but may not work with all games yet. Loading a game the first time without a .gno file present will take 2x-3x longer, but once created the game will load around 10x faster.
Q: I'm stuck with 4 credits, how do I insert more?
A: When in console (AES) mode, you can't insert more credits just like the real Neogeo system. If you push start+select to access the Universe BIOS menu, most games have infinite life/credit cheats listed. Alternatively, to switch into arcade (MVS) mode: open the app menu, change the setting under Unibios Switches, and reset the game. Now push the select button to insert as many credits as you like.
Compatibility List (All sets were tested from MAME 0.144, larger ones require devices with at least 512MB of memory):
Needed BIOS Files (number in parentheses is CRC-32): If you wish to remove unused files in your neogeo.zip, these are the exact files currently needed by NEO.emu
For Universe BIOS mode: uni-bios_2_3.rom (0x27664eb5)
For MVS Japan mode : vs-bios.rom (0xf0e8f27d)
For MVS USA mode : usa_2slt.bin (0xe72943de)
For MVS Asia mode :asia-s3.rom (0x91b64be3)
For MVS Europe mode : sp-s2.sp1 (0x9036d879)