Need Advice on Hitting OG

I brewed a Best Bitter based on a Jamil Zainasheff recipe with slight alterations:

7lbs 9oz Maris Otter
8oz Crystal 120
8oz Amber Malt
4oz Special Roast
Bittered with 1oz Northdown
used East Kent Goldings at 1oz at 10 min and 2 oz at 1 min
2 vials White Labs English Ale WLP002

I mashed at 153 to 154 for an hour and then did a batch sparge . My pre-boil gravity was 1.031 and I had expected to hit 1.039. After the boil I ended up with an OG of 1.038 instead of 1.047 that was calculated in Beersmith. I did extend my boil from 60 minutes to 90 minutes hoping that would help.

I did not check the gravity of my first runnings, and now I wish I would've.

Does someone have advice for anything you do to help make sure you hit your OG?

Thanks in advance.

My first AG I came out low just like you. This time around, I took some advice from the forum. While mashing, every twenty minutes I would rock my mash tun to stir it without opening, and when I batch sparged(which is where I really failed last time) I stirred the hell out of that thing. This batch I brewed yesterday was 15% higher in efficiency. Simple fix made a huge difference.

Thanks! I'll add that to my list of notes of 'to-do's for my next batch. And yes, this was my first AG batch.

In addition to what Ondori suggested, mash with 1.25 Qts/lb and sparge with 2 Qts/lb. I get the target O.G. every time.