Here is little chart that I found years ago that has always helped me, because I've always found it easier to use the numeric permissions in CHMOD.
l r w x r w x r w x
- - - - - - - - - -
4 2 1 4 2 1 4 2 1
for instance if you want to give the owner of a file read permission you would give the file a 400 permission code.
if you wanted to give read write permission you would give the file a 420 code now or for read, write , execute you would give a 421 permission.
Now if you want to add others to the permissions the conventional setup is this:
say you wanted to give permission for the file owner to Read, write and execute and those in His group to be able to read and execute the file but not write to it, you would add the permission numbers together like this:
owner =4+2+1 = 7
Group = 4+1+0 = 5
Others = 0+0+0 = 0
so a permission number of 750 would allow the owner to read, write and execute the file - allow the group members to read and execute the file and others would not be able to read or execute the file.
Here are some commonly use permissions
777 = anyone in the world can read, write or execute the file-- use with caution.
755 = owner can read , write and execute , others can read and execute.
700 = owner can read, write and execute other can do nothing with the file or directory.
you can get other numerical codes by simply added up the permission numbers from the little chart above.
Also I use the -R flag often to change recursively all the permission for the files in a common directory.
hope this helps