Buying lots is the cheapest education available in every other category on this site, and the only way to do it well is a rule you can state in one line.
The rule
Decide what the visible contents are worth to you, and bid that.
Treat anything underneath as a bonus rather than a reason. People who bid on what might be in a lot lose money on average; people who bid on what is in it do not.
Where the first money should go
Small, themed lots. One household, one era, one kind of object. They are cheap, they are easy to assess, and sorting them teaches you more about a category in an afternoon than weeks of reading.
The expensive beginner mistake
Bidding on an unopened box because it might contain something. It might. The price should assume it does not. Buying lots.
The second is ignoring the weight, which decides what delivery costs and is frequently more than the lot.
How to learn without paying for it
- Ask how much the seller has been through — checked, partly checked, or unopened. Three different purchases.
- Ask for the lot laid out and count what you can see.
- Sort everything you buy. It is the fastest way to learn what things are called.
- Keep a note of what you paid and what you kept. After five lots you will know your own hit rate.
What to do with the rest
Resell the parts you do not want, honestly described. That is how most people in this category fund the parts they keep.
Two things to watch for
Restricted items do not become sellable by arriving in a job lot. And personal papers and photographs belong to a family rather than to a sale — take them out. Prohibited items.
Questions people ask
Is an unsorted box ever worth it?
At unsorted prices, with the weight known.
How many lots before I am good at this?
Five teaches you your own judgement. Twenty teaches you a category.
Should I specialise?
Eventually. Lots are how you find out in what.
More: what a lot is worth, questions to ask.