The most common pipeline design error is naming stages after your own activity. Contacted. Demo given. Proposal sent. Each of these describes what you did and says nothing about whether the buyer is any closer to purchasing. A deal can sit in proposal sent for four months while the buyer forgets it exists.
Buyer actions, not seller actions
Rewrite each stage as something the buyer did, phrased so that a colleague who was not on the call could verify it from the record. Instead of demo given, use requirements confirmed. Instead of proposal sent, use proposal reviewed with the person who signs. Instead of negotiating, use commercial terms agreed subject to contract.
The immediate effect of this rewrite is uncomfortable and useful: a chunk of your pipeline falls backwards, because deals that had advanced on activity cannot meet a buyer-based criterion. That is not a loss. Those deals were already in that state, and now you can see it.
Four to six stages, each with a written test
A workable default for a small business runs something like qualified, requirements confirmed, proposal reviewed, commercially agreed, closed. Five stages, each with one sentence describing what must be true to leave it. If you cannot write that sentence for a stage, delete the stage.
Run separate pipelines where the buying process genuinely differs. A business selling both a quick transactional product and a long consultative one should not force both through the same five stages, because the resulting conversion rates describe an average of two different things and therefore describe neither.
Watch for stage skipping
When a deal jumps from the first stage to the fourth in a week, one of two things is true. Either the deal is genuinely unusual, perhaps a repeat customer with an existing relationship, or the stages were applied loosely. Both are worth a question, and the pattern across many deals tells you whether your stage definitions are actually being used.