What I call the "breadcrumbs technique" is basically representing your main experience, as a trail that the player will want to follow -- like a trail of pebbles or breadcrumbs. If we take the example of a narrative RPG that means that you narrative never stops. Party chatter, cutscenes, dialog, events, etc. The player should be following your narration continually, never giving him a rest.
One of the best and recent examples of this is Mass Effect 3; in that game, there is always something happening, narrative-wise. If you are on a mission, every single room of an area will have something to keep you interested: a console with some info, a quick party chat, a point of view, an event like something exploding, or a ship landing, a cutscene, etc. You go from narrative breadcrumb to narrative breadcrumb, then to a big breadcrumb -- a milestone, like the end of a mission, or a huge event in the story. It is a narrative rollercoaster, and when it stops, that's only because you finished the game.
In a Dungeon Crawler that means ensuring that your character and loot progression is permanent, that there is always something to upgrade, often. New shoes, new pants, slightly better shoes -- wow, a massive upgrade for my sword! -- and so on. Your loot system and random number generator needs most of your attention; they generate a big part of your breadcrumbs and should be carefully tweaked, and that's far from simple to do.
Of course the character evolution itself -- levels, skills, feats, attributes, stats, etc. -- needs attention, too. The more ways for the player to enhance his character, the better, and of course with carefully placed milestones, that generates a bigger feeling of progression for the player once in a while, like a level up. This is without forgetting new challenges to put those hard-earned improvements to the test.
It basically comes down to this: divide your experience in small breadcrumbs and big breadcrumbs, and ensure a constant flow of them for the player to follow, with big breadcrumbs (milestones) appearing once in a while to refresh his focus, and make sure that even secondary things bring him back to the main path.
BioWare and Blizzard typically are very good at this, and if we take the Mass Effect series as an example, it even got better at it with each game:
Be careful to not be tempted to add features from other types of experiences just to "please more people." This most certainly won't work.
Most, if not all, RPGs that have attempted this have been received with mild success, whereas RPGs that solely focused on their main experience and making it the best possible have been very successful.
Trying to add a bit of another type of experience brings a lot of chances to simply damage the coherence of your design and experience, dilute it, and scatter the focus of both your production and your player -- and in every case most certainly won't be enough to satisfy the people who like that type of experience, since there won't be any of the depth and ancillary features needed to support it.
I don't know the secret of success, but the secret of failure is certainly trying to please everyone.
Kingdoms of Amalur: Reckoning
Here are a couple of games which tried to mix and match with mild success.
Don't get me wrong, though; there are great things to take or adapt from every kind of RPG. Every time you do so, however, you have to make sure that what you take is going to support your main experience, and not create the tip of a new one which won't be properly supported, feels incomplete, and thus disappointing -- and risks losing your player's attention and interest in the game.
Do you want to make the best chocolate cake, or the best lemon cake?
Trying to make a cake mixing lemon and chocolate might just end being something that pleases neither the people who like chocolate nor those who like lemon. But maybe there are some ingredients from that lemon cake that could enhance the flavor of your chocolate in your chocolate cake? Then by all means, go for it!
In every case, though, be aware that if you start mixing genres this will require an even stronger, innovative and carefully considered design.
So in conclusion, always clearly define your main experience, never lose it from sight, and ask yourself: Are my breadcrumbs clearly defined? Where are they? Do they appear often enough? Do they stop sometimes? Where are my milestones? If you have secondary quests, objectives or features, are they somehow tied to the main path, bringing the player back to it gently?
We've all had those moments where you start an RPG and, after a while, you stop playing it and never finish it, and you can't really put your finger on the exact reason. You are just "not into it anymore."
Usually the reason is that the breadcrumbs stopped, or that the experience as a whole was not focused enough. Ensuring that your main experience, what drives your player, never stops and that they go from a series of small tastes of that experience, to big dishes regularly until they are satiated, will go a long way to help you create a successful RPG of any kind. That being said, you will quickly notice that it is easier said than done, so good luck!