Here is patient UK page on it https://patient.info/health/spirometry-leaflet
In my experience in UK, if you are just having spirometry test through your respiratory clinic at the GP surgery, there are two different breathing methods, one deep in breath with fast exhale and continue exhaling until you can't any more. The other is deep breathe in with a slow steady exhale until you can't breathe any more. Both with peg over nose. the respiratory nurse will explain on the day. Peak flow also.
You can ask for a copy of the results which are good to have and compare against the next test for your own personal understanding and also you can do your own calculation to determine the FEV1% predicted using patient uk spirometry calculator. https://patient.info/doctor/spirometry-calculator
The other tests if you are having them done at the hospital clinic, is usually the full lung function test. where additional tests are carried out with exhaling and the peak flow, its been a while since I had a full lung function test so I can't remember all the detail of that.
The spirometry test I have done annually now, my condition is stable.
People whose condition is not stable, ie prone to ongoing lung infections may be monitoried more often.
With the lung function test done at the hospital, its usually when you have been referred to a respiratory consultant and the results of this test will first be analised by the consultant and results sent to your GP with a covering letter usually, you can ask your GP for copies of the results and covering letter from the consultant.
Personally I have never had a before and after medication monitoring, I guess that's because I of extensive testing before actual diagnosis, and that my CT results clearly indicated my lung damage (its explained more in the leaflet link above under the heading 'reversability testing'
You may have been informed already, in case not, do read the leaflet link above and check out the heading; 'What preparation is needed before having spirometry? '