In this work, we present some simple techniques for enhancing the diversity provided by retransmissions in OFDM and DMT modulations. The primary techniques of interest are symbol interleaving and mapping diversity for retransmissions. Symbol interleaving involves retransmitting packet symbols through different subcarriers of the same channel, while mapping diversity involves adapting the bit-to-symbol mapping for each retransmission. An analysis of the ability of interleaving to produce lower bit error rates is provided. Also, a discussion of optimally adapting the mappings and their application to OFDM and DMT is presented. Simulation results validate the efficiency of these methods in reducing BER and increasing throughputs.