I started by making each petal separately using Corded Brussels stitch and including the odd bead here and there. I'd taken photos and did some watercolour sketches first, to get a feel for the shapes and colours.
Then I attached them together using a simple cordonnette technique.
Here are some links to needlelace resources...
Lacemakerslace
Doreens Needlelace-dot-com
A bit of history and technique
Or you can simply Google "needlelace" and work your way through as I am doing now... Enjoy!