When you're walking a trade show or scrolling a supplier's catalog, the first thing you look at is the label. Does it clearly state nicotine strength? Is it in mg/mL or percent? Both are common—just make sure it's unambiguous. You'll also see whether it's salt or freebase. That matters because your customers expect a certain type. For disposables, it's usually salt. If the label is vague—like 'high' or 'medium'—that's a red flag. You can't sell something you can't describe honestly.

Also check the packaging: is there a batch number? A lot number? If it's there, good. That means you can trace issues back to a specific run. If it's not, you're stuck if something goes wrong.