I use CL exclusively. You need to decide what you're willing to take. Personally, I only buy for 70% or less of the current new item price. I've had good luck selling at 75-80% of new. Include good pics in your ad, product -type pics ('seamless' white background, a piece of paper works just crop tight). Ask for a phone number in the reply.
I use the same method as Neuro above: CL all the way. Ebay works if you're patient and don't mind shipping, paying Ebay fee and Paypal fees...and maybe getting less for your items.
Craigslist has its inherited security concerns with selling expensive items:
I use these guidelines for CL:
1. Never bring a buyer to your home. Meet at a local busy business like Starbucks, etc.
2. Never ship any item and expect to get paid.
3. Talk to the buyer on the phone before you meet.
4. Be honest about the condition of your item.
5. Be realistic about what your fair price is and what the market will bare.
6. Cash only or trade, never a check, cashiers check or money order.
7. Bring a friend if possible to witness the transaction.
5D3, 6D, 1D4, 16-35 2.8L ll, 50 1.2L, 50 1.4, 24-70 2.8L II, 135 F2.0L, 200 F2.8L ll, 70-200 2.8L II, 70-300L, 100-400L, 24 TSE L II, 85 1.2L II, 100 2.8L, ZEISS 100 2.0, ZE 50 2.0, ZE 35 2.0, ROKONON 35 1.4, SIGMA 35mm f1.4, SIGMA 85 f1.4, S110, S100, sony RX-100 and one big-a$$ bag