When to check OG?

I know this must be a big time NOOB question, but I was just thinking tonight as I was finishing up a batch...Should I measure the OG before or after I pitch my yeast? I assume before, because obviously adding a solution of yeast is going to affect the OG. Thanks!

Measure before

Yep, measure before. Although in reality, as long as you didn't scoop up a high concentration of yeast if you happened to do it after it wouldn't be the end of the world. but doing it before will give you the most accurate reading and ensure you don't waste any yeast by scooping them up in the sample.

i always measure OG before I pitch

Okay, thanks guys, that's what I thought, but I'm still learning, so I had to ask!

I dont really understand this gravity thing but mine was 100.30 is that ok

I think you mean 1.030,& that's a little low. Most noobs don't get the wort & top off water mixed well enough to get an accurate measurement. Pour both in the fermenter & stir roughly 5 minutes. That'll mix it well.
And the yeast won't change the gravity,just the sugars,etc in solution. As the sugar gets turned into co2 & alcohol,the solution's gravity gets lighter & the number on the hydrometer scale gets lower.

So what outcome can I expect with a low reading...

If your reading, after a good stir, is still that low you will still make beer. The expectation is simply that you will have a lower than desired alcohol content.

Bummer alcohol is what i am shooting for..Hopefully my reading was inaccurate it was sorta foamy after the stir...

with an extract batch and possible stratification, the low reading is incorrect

as long as you hit your volumes, the OG will be what the recipe said it would be