The approach to trading up is probably dictated by who you either think will draft the player you want, who is also ahead of you in the draft order, or who you think will be selling their picks to another bidder.
Hard to be 100% sure on either front, but probably relatively easy to know who will have enough needs or higher rated alternative(s) to select someone else instead.
The wheeler dealers picking before #14 and already looking to trade down are likely known to the teams, but not so much to Joe Public.
The riskier propositions are those teams who want a particular player or players, don't get them on the day of the draft and suddenly turn into sellers. That's the wild card. For example, if Minnesota can't trade up higher and don't get their guy at #11 (or Denver at #12), or if the Bears don't like the options at #9, do they look to trade down and add assets?