FPGA BASIC
Here's my approach. Maybe you have already done some of these steps!
1. Learn digital hardware design.
2. Learn an HDL such as Verilog or VHDL.
3. Buy an inexpensive FPGA development kit from Xilinx or Al.tera, and try the example projects.
4. Create your own small experimental projects.
5. If using Xilinx, read your FPGA "User Guide", and the "HDL Coding Techniques" chapter in the "XST User Guide".
6. Read Xilinx or Al.tera application notes describing more advanced FPGA techniques.