Mike,
The best way to get grill marks are as followed. M<ake sure you pre-heat your grill for at least 10-15 minutes. You can try using lump charcoal which does burn hotter than a traditional briquette. You need at least 500-550 degrees in order to sear a piece of protein. Also, a nice light coating of olive oil on the food you are grilling will also help with obtaining great grill marks. Finally, the Gourmet BBQ system sear grate is a great addition to a Weber kettle which will also help you obtain out of this world grill marks.
Grate question
Kk