99 Silverado Electrical Issue?

I have been having trouble with the truck going completely dead when I turn the key to the start position. Everything just goes dead. I was told to disconnect he battery and reconnect - before starting or using any electrical power, press the unlock button 3 times within 5 seconds. At first this worked and the truck would turn over and start. But now it just clicks once and is dead. No lights or dash lights. Any ideas anyone?

double check the battery connections, they have to be clean and tight. you might have something killing your battery or a bad battery. does it start off a jump? make sure the alternator wires and starter wires are tight. as well as where the negative battery cable attatches to the block.
good luck