just make sure you have got plenty of backup tickets so you can vary your routings and fly with other carriers if necessary.
Good advice. Especially for longhaul.
It can be quite surprising the carriers that link up to solve your offload problem.
Take details of schedules too as it reduces the risk of choosing a bum connecting point or wrong flight frequency.
Annoying details like BA flights to South Africa operating from different terminals can affect plans.
Rival airlines often operate from diffent terminals so that too reduces options.
Keep a sense of humour you may well need it.
I had three round trips to LHR for my last longhaul flight and only got away due to a "suspicious package scare" that caused in coming connecting pax to remain seated ( not allowed into the terminal ) while I got their onward seats.
As has previously been stated, many airlines dictate a years service prior to concessions although I think the industry says minimum of six months.
Hopefully the company may provide load predictions for its own flights.
Else if you are not allowed access to reservations data then you need to find someone who can else you are going to be planning blind.
When it works it is great. enjoy.