Most games have the function to save your current status, in a file on to your hard disk. This is an obvious weak point in any games attempts to stop you from cheating. Once the games status has been saved, it is easily accessible and vulnerable.
Another thing that games tend to have in common is a 'score' of some
type. Whether this is money, points, lives or whatever is unimportant
as they will all be stored in the same way.
So the easiest thing to do is to take a note of the current values used in the game, save it and then open it in a hex editor. Any hex editor is fine, there are plenty of shareware ones available on the net. One problem you may have is finding the correct save file.
Quite often, it will be placed in a directory called 'Save' and will simply be a list of files in order of time. So your first save game will be the first file in the list, and so on. It may be listed like file1.sav, file2.sav, file3.sav etc. which is easy enough to locate. So, once you have your file, open it up.
Now comes the slightly trickier part. First of all, you will need to
convert your score into hex. Some hex editors have this function
built in, otherwise you can use your own calculator, or even the
calculator in Windows. Of course, you could do this yourself, but I
generally can't be bothered, especially for big numbers.
Next up is reversing it. "Reversing it?" you say! Yes, because of the way numbers have traditionally been stored, the high bit is stored on the right, and the low bit on the left. It does make sense if you have a degree in computing, but not otherwise. But make sure you reverse it in byte pairs! For example:
Score = 1258
Hex score = 4EA
Reversed hex score = EA04
(Note: 4EA is really 04EA (It must be a pair))
Once you have this value, you can do a search on it. Make sure you enter it in the Hex box, and not the text box. No point searching for a string if you want hex. If you find a match, great. Keep searching. Once you have all the matches (hopefully not too many (hint: Searching on values less than 256 decimal is not advised)) you can decide which one is correct. This can either be trial and error (backup your save game) or it may be obvious. For instance, RPGs tend to store stat information about about each character next to the name. When you've decided you have it, change all the digits of the score to 'F', or '0', depending on whether you want a high or low score. Then save the file, load it into your game, and see if it has worked. Good luck!