setting keep-alive to 0 will reduce the amount of load on the server , blocking bad or unknown user-agents and setting low max request size will help.
Here is my lighttpd config
server.even-handler = "linux-sysepoll"
server.network-backend = "writev"
status.status-url ="/server-status"
server.max-fds = 9096
server.max-keep-alive-idle =0
server.max-keep-alive-requests=0
server.max-request-size=10
server.max-write-idle=15
Here [i own this domain ] you can see Lighttpd standing on a medium layer7 attack.
I hope this config helps you ,
Regards.