First off, I am not the world's greatest detectorist, or the most experienced, only had my X-terra 705 a couple of years, but I prefer detecting for gold than sluicing tons of material. I've learned some things that hopefully will help.
I would keep your expectations very low. Expect nothing other than a really great time outdoors, that way you won't be disappointed. Persistence is the key. Just get into your zen...
I strongly recommend wearing good gloves, as even the grasses in the desert are needle-like and it's fairly painful to get a palm full of the microspikes which are hard to remove (I also carry a good first aid kit in my backpack-I use it all the time...also be sure ot bring spare batteries-so many people I know finally reach their BFE spot, but then run outta juice!). One of my first times out, I wasn't using gloves and tumbled down a hill into yucca leaves (they are as sharp as hypodermic needles, and hard as steel). Although my hands were speared (lots of blood too), no veins or arteries were hit-a good pair of leather gloves would have prevented the worst sticks that day-oh well, lesson learned.
From my experience, most of the placer areas (or any areas where humans have been) have been worked and re-work numerous times in the past 150 yrs and are heavy infested with trash. Expect to dig a lot of junk before you get something really good. It's pretty amazing how far those aluminum fragments blow in the wind. If you can hit the tiny bullet fragments, bits of wire, lead pellets...and more importantly, quickly recover them (because you'll be digging tons of targets), you should have no problem hitting on gold (if it's there). Do not ignore weak signals, which should get louder as you dig deeper. I've dug targets 12" down (at least), but most are within the top 6". It just depends. Be sure to re-detect your hole after finding a target, sometimes there are multiple targets. If there are old detector holes in your area, re-detect them...people can often miss a target for various reasons.
I would recommend using prospecting mode in default mode using the 6" DD HF coil (I love that it's waterproof). If there's little trash in the area switch over to the 10X6" DD HF coil as it is really great for covering more ground.
I normally sweep in prospecting mode choosing areas with exposed (or shallow) bedrock or work exposed tertiary riverbed cliff faces (watch for falling rocks). You can switch to all metal or a pattern for target ID. I like to leave tracking on, auto GB, auto noise cancel. You can work a section in prospecting mode, then re-sweep in another mode. Go slow. If there's virtually no trash (like some of the areas I work way up the mountainsides), it can be boring, so be sure to test some trash from time-to-time and rebalance too. IMHO, the auto tracking does a great job of maintaining balance, but I still re-balance from time-to-time. I will turn off the auto track when pinpointing and digging targets. I have not blanked out a target with the auto GB tracking on, but I still turn it off when I dig.
I know successful detectorists who strongly recommend detecting in AM, with no iron mask. I personally like the mask, which will blank out ferrous items. Do you have a test nugget (mine's wrapped in a plastic baggie, others use them on poker chips, etc), which you can then bury in the field to test your set-up. Try putting rocks over it too-I was surprised how sensitive and deep the X-terra 705 is on my small nugget.
Depending on mineralization, you may need to drop your sensitivity to get better stability, don't worry it's normal. I recommend digging all targets, and expect to find some hot rocks depending on the location. I like to pack out all the trash, and I re-work areas many times. Any place near roads will be trashy. Adit entrances can be very trashy too, try drywashes and gulches above and away from the mine. Sometimes, I've hit an area that is so hot, that my machine will blank (the area was hydraulic mined). It's sometimes easy to get date a site based on the old debris laying around (like the piles of food cans). If a site has not been hunted too hard, there will be more trash targets, and thus an increased chance at finding good stuff. See those tailing piles....they are AWESOME. Detect and move the rocks (or rake them). Repeat for many happy hours. The tailings in my area are with large rocks, so they were used as trash repositories by the old timers. You can find surprising things in them, but beware of all the critters living in the cracks!
P.S. The desert sucks the moisture from my lips. Lip balm is great and lightweight. Also, some good DEET spray is a must. Ticks can be found all over the place, you just never know.
P.P.S. It may seem obvious, but I suggest detecting spots where people have detected nuggets before. If you are detecting an area that's mainly known for fines and flakes....your odds for find larger gold may be lower, and thus it may take you more time to hit a picker.