Ask 100 pilots to give an approach briefing and you will get 100 different briefs.
Here are the 5 essential elements that I have come up with for briefing each approach I fly.  As a rule I brief everything on the chart, but these items are what I make sure to emphasize to ensure a successful outcome.
(Note: this is not intended to be everything needed to safely fly an approach, do what is right and prudent for your situation.)

1. Airport name and approach procedure.

If you start looking for the approach to Springfield, how many plates do you think you’re going to find? The answer is a lot. At least 5 or 6 off the top of my head. Trust me, it’s easy to get Springfield, Missouri and Springfield, Illinois mixed up.
How many airports start with the heading “Seattle”? Boeing Field (BFI) and Seattle Tacoma (SEA), but which one are you looking at?
How about the approach you are doing?  It’s really easy to mistake the ILS 02R for 20R if you’re not careful.

2. Approach NAVAID and frequency.

If an ILS has a frequency of 121.8, you’ve done something wrong.  There are a lot of numbers listed on a chart, it’s easy to transpose them if you are task saturated.
It’s also really hard to fly a glide-slope when there isn’t one for your approach.  I’ve thought I was on an ILS when it was only a localizer, and I’ve flown with pilots who have waited for a glide-slope on a VOR approach.

3. Approach course.

This goes back to the runway 02R and 20R.  If the controller gives you a heading that looks backwards, it may be time to check your course, or reset it all together.

4. Minimum descent altitude / Decision Height

This is as low as you can go, period.  Know where to stop your descent.  I’ve seen pilots who have descended hundreds of feet below MDA because they did not brief the MDA, and many pilots who have blown right through MDA because they couldn’t stop a descent fast enough when they realized what it was.

5. Missed approach initial climb.

You don’t need to memorize the whole missed approach.  You can’t, and you won’t unless you fly the same exact approach every day.  You do need to brief and memorize the initial climb that will get you out of harms way should it become necessary.  Once safely climbing away from the ground you can glance at the next step in the missed approach.

Notice I didn’t include step down altitudes or minimum safe/sector altitudes.  The MSA is something that can be referenced later if needed.  It is not a normal altitude to be flown and would only be used in emergency scenarios.
Step down altitudes can be briefed as part of the MDA, but generally I talk myself through the step-downs and memorize the MDA.  Sometimes there are just too many step-downs to make without referencing the chart.
Most IFR pilots flying alone silently brief the approach to themselves, but it might be good habit to verbalize what you are looking at. If you are flying with another pilot, it is crucial that both of you are on the same page and understand the approach.  You can never be too familiar with an instrument approach.  Every review, verbalization, and brief helps.
I know there will be a 100 different responses about your top 5 briefing items.  I look forward to hearing them.