Decoding instruction using opcode and function bits

Question

I am trying to design a pipelined-cpu-simulator. As a part of that i need to design a control unit.

What i am expecting the control unit to do is - to set the values of following flags:

reg_write (=1 if the instruction writes a value to some register, =0 otherwise)
mem_read (=1 if the instruction reads a value from memory, =0 otherwise)
mem_write (=1 if the instruction writes a value to memory, =0 otherwise)
jump (=1 if the instruction is a jump instruction, =0 otherwise)
etc.

I need to set these values as a function of the opcode and function bits of the instruction. How can i do that?