Ok.. This is a typical basic F:line
F: Username Password 2 0 0 { 0:0:2 }
OK.. So i will try to explain the highlighted bits in each line :
F: Username Password 2 0 0 { 0:0:2 }
This is obviously the username you give to your client so that has access to your card..
F: Username Password 2 0 0 { 0:0:2 }
This is the unique password give to your client to give him access to your card..
F: Username Password 2 0 0 { 0:0:2 }
This client will get all cards at a maximum of 2 hops away from me.. I always set to "2"
F: Username Password 2 0 0 { 0:0:2 }
This number is to allow emu`s.. Which i always set to "0"
F: Username Password 2 0 0 { 0:0:2 }
This number is for setting the allowances for EMM`s.. Which i always set to "0"
F: Username Password 2 0 0 { 0:0:2 }
This setting is to set the caid:id(:downhops).. Again.. I always set to "0"
F: Username Password 2 0 0 { 0:0:2 }
This setting is to set the caid:id(:downhops).. Again.. mine are always set to "0"
F: Username Password 2 0 0 { 0:0:2 }
This setting is to set your down hops.. ie.. your user and 1 more hop away from me..
Hope this helps the newbies who are not sure how to write f:lines
thanks SHAHID GEO for explaine and nice info keep posting for member to guide here. 
