Here's the official BBO description of the levels in each case followed (in italics) by my take based on actual experience:
These BBO descriptions of course beg the question: what defines success? Do you have to win a major national tournament event to be an expert? Or is it sufficient to have placed in the overalls, or got a section top? What about bracketed KOs? Must you have won the top bracket? What about Midnight KOs? What about single-session consolation events like a Swiss? I think it's all just a bit too vague.
Someone who recently learned to play bridge — like, today, er... just now.
Someone who has played bridge for less than one year — more like less than a month and may not have played at a club.
Someone who is comparable in skill to most other members of BBO — someone who is reasonably honest about their skill level but who hasn't really progressed much from the beginner stage.
Someone who has been consistently successful in clubs or minor tournaments — someone who has been playing too long to describe themselves any other way.
Someone who has enjoyed success in major national tournaments — someone who can count to 13, especially in the trump suit; may actually know what an endplay is and perhaps has actually pulled one off; knows that underleading an ace at a suit contract is generally a bad idea.
Someone who has represented their country in World Championships — a real expert.
So, I've been compiling a list of the types of errors that I see perpetrated by the various levels. Many of these observations come from individual tournaments, or just sitting at a random table (although it's rare to find anyone who claims to be an expert sitting at such tables — I only do it when I don't have time for a real game). So, here goes:
- Fails to notice that an opponent has shown out of a suit and/or fails to appreciate that said suit is now going to block if we aren't careful.
- Thinks that the double of a 1NT overcall is for takeout.
- Discards potential winners instead of likely losers when declaring a hand (one suit is 97 opposite AJT6 [two tricks are certain], the other suit is AQ87 opposite 543 [82% chance of two tricks]).
- With ♠Q9654 ♥AK ♦95 ♣KQJ4, after this auction (IMPs, none vulnerable, dealer is on the left): p p 1♦ 1♠ 2♦ 3♦ 4♦, prefers to bid 5♣ rather than waiting to see what partner is going to do (result: -100 instead of +420).
- Bids 1♠ only with ♠AJ62 ♥AJ86 ♦5 ♣KJ64 when (all vulnerable) LHO opens 1♥ and partner doubles.
- Raises partner's 1♠ (previous comment) to 2♠ over an intervening double with ♠Q843 ♥75 ♦AK864 ♣Q2. [This pair bids all the way up to 4♠ but opener's partner has KT975 of trumps and wields the axe for a top. (or 8 IMPs if it were teams)].
- Deals and opens ♠AK8 ♥void ♦AQJT9862 ♣A2 with a diamond preempt.
- Doesn't notice that this is a 1NT opener, playing SAYC: ♠752 ♥J765 ♦AK5 ♣AK6.
- Despite having no entry while defending 3NT, and despite dummy positively bristling with winning black cards, continues a third trick in own suit (hearts) which is 100% sure to be won by declarer rather than switching to diamonds which would win his side two more tricks.
- With this hand: ♠AJ64 ♥J952 ♦Q95 ♣65, and hearing the following auction (none vulnerable, starting on your left): 1♣ p 1♠ p 2♠ Dble, decides that this is a good time to penalize those pesky opponents and passes — result -470 instead of -100 (or -50 or +50).
- With this hand ♠Q763 ♥K5 ♦AKQJT ♣T3 (vulnerable vs. not) after one pass on right: 1♦ 2♣ p p 2♦ Dble p p p. Dummy comes down with ♠T954 ♥T643 ♦9 ♣AQ95. The lead is a trump which you have to win in hand. You are very fortunate in having two club stoppers which will give you time to establish a spade trick or two. But the first thing you do is to use up those club stoppers so that you have to use your good trumps to swat clubs instead of establishing your own tricks.
- Believes that a balanced 18-count is enough to bid a major suit game opposite a single raise by partner at matchpoints.
- At favorable vulnerability with ♠QJT8652 ♥void ♦AK64 ♣T9 overcalls 1♥ with 4♠, then after 5♣, double, 6♣ [sic], naturally rebids 6♦.
- Over 4♥ by RHO (nobody vulnerable, Goulash hand), bids 4♠ with ♠AK98 ♥A ♦53 ♣KJT764.
- The only way I can do this advanced player justice is to show the whole hand (from an individual):
Note that I made five calls during the auction: two redoubles and three doubles. What fun! If you click on the GIB button, you'll see that as long as I start with a high club (what else?) we are destined for +500. Unfortunately, it's now necessary to switch to a low spade to keep our 500. That seemed contraindicated to me so I switched to the ♥J. Down to 300, although I'm still on lead and now any small black card will get us back to 500. I'm fairly keen to avoid setting up a winner in dummy because I want to protect my partner's diamonds. Alas, I continued a heart. Partner gets in and at trick 5 he plays... a small diamond! A two-trick error. Wasn't it blindingly obvious that declarer has the missing diamonds? At this point, we have gone from +500 (an 83% board) to -490 (a swing of almost 1000 points and a 0% board).
- Holding ♠J97 ♥J93 ♦KQ4 ♣AJ54 (none vul) and having dealt and opened, after the auction (opps silent): 1♣—1♥—1NT—2♠, passes (not a tragedy because about a third of the declarers in 3NT went down).
- Holding ♠AKQ53 ♥JT76 ♦742 ♣J (all vulnerable) and hearing partner open 1♣, responding 1♠, hearing double by LHO (a passed hand) followed by pass and 1NT, decides to bid 2♠. [When the same auction happened at another table, a real expert doubled for blood and ended up with 800].
- Holding ♠J9 ♥Q52 ♦AQ6 ♣AK983, having opened 1NT and hearing partner transfer into hearts and then bid 2♠, bids 2NT [The opponents mis-defend but we still get a poor score because everyone is making 10 tricks in hearts, some in game, some not].