As you come into the anchorage, look where the boats are situated compared to the chart. As you get further in and begin to search for a spot to drop your anchor be aware of the depth and look at what the other boats are using for gear. It's not hard to spot those boats with all chain vs chain/nylon rode.
The distance from boats is dependent on the depth, expected winds, and type of anchor rode. Generally you can get away with 3:1 if you use all chain or 5:1 if mixed rode in light conditions. Don't forget to add the height of your deck to the overall calculations (ie. depth is 10', deck height is 5', so a 3:1 scope would be 45' (10+5=15x3=45'); not 30').
In a perfect anchorage, all chain boats are anchoring away from chain/rode anchors. In the real world the helmsman needs to assume all rodes are in the 7-10:1 range. You don't want to be anchoring on top of another anchor or caught in their rode. In a lot of anchorages you can simply look over the side and see where the rode and anchors lie.
Feel free to check out the anchorage. Spots that boats are in may not be the spot that looks good to you.
The person on the bow is looking for a good spot (no coral, grass, garbage, other anchors/rode) while the helmsman is monitoring the depth. When you're rode length + 2x boat length from the nearest boat, tell the bow person the depth and follow their direction.
Working as a team, the bow person directs the helmsman to the designated spot. The helmsman will indicate when the boat is far enough upwind of the boats behind them. When the bow person selects the spot they direct the helmsman to stop and the helmsman responds with the indicated depth.
The idea is to come to a complete stop, bow into the wind, over the position selected by the bow person. That person will immediately lower the anchor and chain in a controlled manner (no dumping it all in a pile). The boat should now be starting to move back slowly. At the determined rode length, cleat/secure the rode and wait. The mass of the boat should gently allow the anchor to dig in and the rode should keep the pull parallel to the bottom.
With the bow person monitoring the rode, the helmsman puts the boat in idle reverse and gently pulls back on the setting anchor. Too much pull or too sharp a pull and the chances of the anchor pulling out, requiring a reset, are highest at this time.
Look behind you to make sure you're not too close to the boat behind you or too close to boats to either side of you. Give yourself extra space in case the wind pipes up at night and you need to let out more scope. Don't count on the boats around you to add more scope as they may not or may not let out as much as you want.
If idle reverse shows that the boat is secure then increase the RPMs until you're sure the anchor's set. Secure the boat. Mark the position visually and on the GPS. Set the GPS anchor alarm and zoom in as far as the GPS will allow. Record your position in the log (of if you're anti-log, on something that you can refer to). Also record the wind speed and direction.
What you want to see is a big smile. As the boat moves in the wind, she'll move from side to side, ahead and astern. These wanderings will be recorded on the GPS. There will be several lines as wind, wave, and boat motion aren't always consistent. What you want to see is that the smiles don't walk down the GPS ground display.
You're almost there. When the boat's apparently secure, don mask, snorkel, and fins and dive the anchor and rode. You're looking for the anchor to be well dug in, no chain wrapped around coral heads or garbage, and the pull in line with the anchor shank. Spend a couple minutes looking at the setup, allowing the boat to move a bit. The anchor should not move and the pull of the boat should be as close to parallel to the bottom as possible. Too much angle indicates too little scope and increases the chances of pulling the anchor out.
Back on board watch the boat movement and find two reference points on land or two compass headings that appear consistent. This will be a visual indication to back up the GPS. Record these.
Now as you go about your business, check the GPS occasionally, look at the reference points/compass bearings, and boats around you. Be pleased that you now have the best spot in the anchorage as all other boats want to anchor too close to you.