My favorite airport to watch aircraft is at KPDX because you can see all the aircraft and there are multiple spots to watch the aircraft from. Such as…
• Marine drive (In between the water and the airport fence)
• Floor 7 (Short term) parking garage)
• NE 82nd way 9 (side of the road)
Here is a few tips…
• Try to back up from the runway so that if your taking videos OR photos you can keep the aircraft in view the entire time.
• Use some sort of flight tracking system such as Flightaware or Flightradar24 so that you can see if anything special is arriving and/or departing.
• Try to position yourself away from structures which obstruct your view and/or mess up the photo/video.
LAS. Best place to planespot. There’s a dedicated viewing area on Sunset Road, parallel to 26L and 26R, with ATC broadcast on FM radio straight to that viewing area, so you can listen to Tower on your car stereo, plus use LiveATC or a handheld scanner to pick up any other frequency in the entire Las Vegas Valley.
Additionally, VGT (North Las Vegas) has a similar viewing area, but is also a park with a playground in the viewing area. It also has ATC broadcast to that viewing area. It’s on the corner of Decatur and Lake Mead Blvd, between the approach ends of runway 7 and 12R.
BL.
That is interesting, I did not know that! May have to go to Las Vegas sometime.
Have a look at it on Google Maps. Link is here:
You can see where it exactly is in relation to 26L/R, as well as being able to see the stream of arrivals coming on final into the area. Plus looking to the west, you can see the arrivals going into the 19s, with the casinos behind them.
VGT is nearly the same:
Not many airports have dedicated spotting areas here in the US, let alone ATC fed directly to them, so that makes these spots the best in the country, in my biased opinion. 
BL.