MySQL replication: most important config parameters for performance on slave server?

I'm setting up a mysql master-slave configuration, where slave is located on a much weaker sever.

Since, if I understand correctly, slave only works on updates/inserts, what are the most critical configuration parameters that I can adjust in slave's my.cnf to ensure best performance and smallest possible latency?

• Master: 32Gb RAM, Slave: 4Gb RAM
• Mostly innodb tables
• Percona-server 5.5 on both master and slave