Close editors automatically
Window -> Preferences -> Editors. Select “Close all editors on exit
Close all editors on exit [If you don't want to maintain state]
Window -> Preference -> General -> Editors and select “Close editors automatically”
[ Don't select Restore Editor on start up]
Close unused projects
Go to the Flex Navigator pane on the left. Right click on unused projects and select “Close Project”
Disable code folding [In most cases we will not use code folding]
Go to Window -> Preference -> Flex -> Editor. Uncheck “Code folding”.
Use memory monitoring plugin
help->Software updates -> find and install -> search and install -> new remote site (add your url here)
I hope there are many memory monitoring plugins for eclipse.
I am using the following one
http://www.kyrsoft.com/updates/
Tags: Flex, Flex Builder, Perfomance tips