Leroy 1937,
Congrats. on your 705, It's a great detector and I am sure you will love it once you familiarize yourself with it. Although you should read the manual thoroughly, as a new 705 owner, I will give you my tips on starting out. First of all, set sensitivity down to 2 or 3 and then auto noise cancel once you are out on a site you want to hunt. Then, auto ground balance. Make sure that when you noise cancel and ground balance, you are on a clear patch with no target ID's below. Then, I would suggest that you raise the sensitivity sufficiently high without any chatter. As a newby to the 705, I would hunt in pattern two in the beginning which will eliminate iron and many trash targets. Also, don't forget to adjust the volume control depending on whether or not you wear headphones and finally, I would suggest using multi tones so that you can get used to the different sounds that individual TID's make. In time, you will learn the particular's of the machine and can experiment in different patterns, etc. As far as a coil, I began with the standard 9"- 7.5 Mhz but since have purchased the 6"-18.5 DD Mhz and have found a lot more deep silver coins.
HOpe that this helps and Happy Hunting
Chuck