finding stump height

I am running a string line first for levels
and am about to put my new stumps in for my extension.

I am looking to tips what to do and what not to do.

Thanks

That's a broad question!

Set up hurdles along the end and spend some time getting the perimeter markout square.
Mark out where your post holes are required with spray paint.
Hire a dingo with an auger.
Dig holes.
Get inspected.
Then it will probably rain, so empty water and re-dig out all the mud! :)
I did the perimeter stumps with a water level, then ran string lines as a grid to fill in all the centre ones (depends how many you have to do I guess). Hint - laser level is much better if you can hire one.
After all set, hire laser level and double check ... pack with cement sheet if required.
Put down bearers ... then all upward from there.

yeah we used a laser level too. Works a treat once u get the outside posts done. THen stringline is the way to do the inside ones.