We went for sunrise. We left our hotel at 4:45am and arrived at the gates about a minute before it opened. I had read a travel blog about where to stand so we headed straight for the very left corner of the left reflection pool. We had a great eat spot as watched the skies change as the sun came up. We visited in July, unfortunately there was quite a bit of cloud cover so although the changing light was amazing there was no glow or change in the colours of the temple.
We took breakfast boxes from our hotel but there are many local options and annoying spruikers as you attempt to enjoy the serenity.
After sunrise we took a guide. We had planned on doing alone ( family of 4) so had a private car booked by our hotel for the day.
Used a guide once there after sunrise. There are many guides there and all uniformed. No idea if they are official though. We paid $15US FOR 1 1/2 hour tour. So glad we visited.More