You should listen to Mrs Small. She is far younger than me, and far more careful.
What it's probably going to come down to is this: There will be charts that you blow. Occasionally, you won't be able to find a reason. Not often, but it happens. Most of the time, your mistake is crystal clear in hindsight. You aren't likely to make those particular mistakes again. Those things will end up on your personal 'things to look out for' list.
Sometimes, maybe even often, you'll get it right, but you'll miss some important details. These charts, too, contain the answer, and why you missed that huge obstacle the querent had to go through to get what they wanted. Your list of things to look out for will get a bit bigger with this stuff, too.
Many of these things are the classical considerations before judgement. (There was a point to my ramble.) Some of them aren't, but they're still important.
Read Sahl. Read Bonatti if you can. Struggle through Lilly. They'll give you a good idea of why they consider those things important, and for the most part, it will ring true.
For me, personally, the biggest consideration is finding the question behind the question. Sometimes people ask what they want to know. A LOT of times they don't want to know the future, they just want to know that everything is going to be okay eventually. WHEN will I be in a relationship? WHEN will I be rich? WHEN will I have a child? WHEN will I get a job?
Maybe those things won't happen for your client. They may not. And they really aren't the question. You can't assume that much in horary, it doesn't work. It can be more subtle than that but that's the wrong kind of question you're likely to see most, or at least I have. It takes some people skills to deal with that, which I hope astrologers, of all people, do learn.
Get as much experience under your belt as you can.
I don't know any other way of doing it.