Attention filters information from our senses and focuses on only what we want to focus on, much like a satellite dampens most frequencies and amplifies desired frequencies.  

Psychologists describe two main ways in which this works: through stimulus-driven attention (our sensitivity to what we hear, see, etc.) and goal-oriented attention (our ability to focus).  Effective learning as it is typically understood comes from strengthening our goal-oriented attention.  We learn well when we focus (our attention) on one thing at a time.

Different people hone their attention in different ways: meditation, medication, visual tracking, motivational strategies like gamification, or most simply: put yourself in a distraction-free environment.  

"The true art of memory is the art of attention." (Samuel Johnson, writer)

"Attention is the holy grail... whatever you remember and forget depends on it." (David Strayer, psychology professor)

Encoding : How to Make Memories Stick

Encoding is what happens when what you pay attention to meets the brain.  It's influenced by two things: what you already know, and the sensory or emotional strength of what you're paying attention to.  

It's easy to learn new ideas when we can attach them to things we already know.  Let's call this "prior knowledge." The richer our prior knowledge of a subject, the more connections we make to new material, the better we learn new material.  So: want to learn more effectively?  Make connections between what you're learning and what you already know.  

Most people on Quora are in tech, so we encode information about the tech space easily, because we know a lot about it, and therefore we remember it more.  But, we may not easily encode information about knitting (unless you're also a knitter), because of a term like "double crochet" doesn't mean anything to us, so we forget what it means.

The other main way encoding happens is through rich sensory or emotional experience.  This is why it's best to learn things hands-on, experientially.  If we have no prior knowledge of a subject, we learn best by seeing, hearing, feeling, smelling and more.  Describe knitting verbally, and we're lost, but put knitting needles in our hands and walk us through a pattern, and we learn.  In this way, learning through experiences that involve novel or amplified sensory stimulation, that tug the heartstrings or stimulate the libido, or, perhaps best of all, are simply pleasurable and fun--these also enable strong encoding.  

Storage (Memory)

One of the most important factors in building strong, long-term memories is sleep.  Sleep affects how well we store memories.  In fact, we actively consolidate memories while we sleep, particularly the night after we form the memories.  
Roughly, this is what happens, by hours of sleep :
Hours 1 - 2 : we consolidate memories in short-term memory (hippocampus).  
Hours 2 - 6 : we move memories from short-term to long-term memory (cortex).  
Hours 6 - 8 : we actively rehearse memories (cortex).  

So, if you're not getting six hours of sleep, you're losing memories.

But the cool part is what happens next.  After six hours, the brain actively rehearses memories--and makes them stronger.  People perform better on tests of memory when they sleep eight as opposed to six hours--without spending any more time reviewing material.  And, that sleep also provides new insight into the memories.  In one study, people who slept eight instead of six hours were 1/3 more likely to find shortcuts to complex problems.

This all happens while your head is on the pillow.  Want to learn effectively?  Sleep more.  You'll also be significantly more attentive, which strengthens the process from beginning to end.

Retrieval: 
Lastly, every time you retrieve a memory, you make it stronger.  This is why repeatedly studying material over time works.  A guy named Ebbinghaus ran some really interesting studies on this over a century ago.  They're worth checking out.  What does retrieval do, but bring information back to attention, re-encode it, and set up another opportunity for storage.  A virtuous cycle.

What about the humanity in all this science?  Well, the good thing is that this all happens whether we think about it or not.  There's a lot of talks recently about non-cognitive skills, or dispositions, or character.  It's the same conversation, though.  

Students who show curiosity, they're intrinsically motivated to focus their attention on new things.

Students who are creative, they richly (elaboratively) encode information by reworking it, reshaping it, and sometimes engaging with it in multi-sensory ways.

Students who show grit, they're the ones who sit down and work through the whole cognitive cycle again and again.  This gives them more opportunities to recall, understand, and interpret the information.

Want to learn effectively : ask questions (curiosity), play with the material (creativity), or simply return to it again and again (grit).  You'll learn it.