Anyone doing this any length of time is already likely in this realm and this won't be a tip for them. But if you are new to this as I am to this particular aspect of wildlife management I've got a case I just went through that could have been a very negative outcome.
I just finished a large apartment complex pigeon exclusion, all swamp cooler ductwork parapets, all stealth net product installed to exclude the birds and of course clean up prior to installation.
I don't always carry a true camera around anymore, as frankly I've dropped so many in the last two years that my wife pretty much ruled it out!

However my iphone takes great pics, plenty big enough size wise for proposals and summary reports and thus, I take tons of photos (way more than I think I need) and download them into iphoto at home each day or week depending.
So this exclusion / mitigation was for 5 different buildings and a multitude of nets. I organized my proposal by each building and parapet and give the issues for each on the summary based on my inspection.
Now where the issue comes in.
I finish the job about 10 days prior to their annual swamp cooler tune up, where they replace filters and such. So they start on building #1 and mention to the manager that there are pigeons there nesting under one of the units. The manager is thinking, but we hired that guy to exclude building #1.
What he fails to see is that in the proposal I inspected that pit and showed photos of it being free and clear of issues at the time of inspection (this doesn't mean a pigeon which can turn a new area into their own personal property overnight can't turn up at any time after the inspection).
I did work on building #1 but what they needed and received was exclusion of their large company sign that is mounted on the front of the building. There were 4 nesting pairs in this structure and it received bird wire on top to prevent loafing/roosting and exclusion netting and materials around the sides and other entry points.
Additionally the gutter which is under this structure was full to the brim of droppings and the roof was coated leaving this to fall below onto the walkways and stairs of the units. This was all removed, cleaned and remedied as requested and as performed.
Now, when he called me to inquire why his guys see a pigeon nest as he knew this building was an issue, I mentioned calmly, this building was a problem because of the sign and explained how many pairs were in this. I also said, let me look at my pictures and reports and I'll get back to you. I didn't argue with him or get uptight.
Upon looking at home, I had a series of photos that showed this parapet was free and clear, I had photos from under each unit and all nooks and crannies pigeons tend to use.
The result, a bit of explanation, an extra page of photos added to the before and after summary and I still have a happy satisfied client.
So my tip is, take lots of photos and have an airtight contract written to explain exactly what you are, and even what you aren't doing.
This place has 20 buildings, with 2-3 parapets on each building, they all have pigeons, but only those I worked on were enough of a problem that they tenants were complaining. Their goal over time is to block all these areas and complete a complex wide eviction.
(Disclaimer - Some might say this would be remedied by removing the birds before exclusion, I can tell you that each building of the 20 has pigeons, more than enough to fill the voids, all looking for places to nest, so while lethal might remove some "pressure" you'd be doing a lot of that just to get enough reduction to maybe reduce pressure in a case like this one and no telling where the new pair came from, though I suspect they moved 30 feet from the primary problem area.)
My main point, is write a tight list of what you are doing, keep to that list as best you can, and remind the clients when they are signing up what is and isn't included and above all what to EXPECT afterward!
Justin