I recently passed my check ride and just like a lot of people here, I couldn't wrap my head around holds for many, many hours. After a while I finally did get them conceptually on paper, but entering them was another story. By the time I took my ride I finally had them down. Here is what works for me.
Or course whatever works for you is what you should stick with, but I threw away all mnemonics and contorted fingers superimposed on the HSI. What I found that worked like gangbusters was found on some site somewhere. It only works if you can draw out the hold itself.
On a 3x3 cube of Post-it's, draw the hold. Make sure it has the fix and the racetrack correctly depicted with the outbound and inbound headings as well as a straight line through the area which will determine the teardrop/parallel area along with those headings. In all you will have 4 headings written down.
Assuming it's drawn out correctly, hold the Posit-it up to the HI or HSI and turn it so that the numbers on the paper lineup with the same headings on the HI. This will instantly show you your orientation from your present heading to the hold fix and whether you are coming in from the small side (teardrop), the wedge (parallel) or direct entry. For example, say you were given the following instructions: "Hold west on the 270 radial". You would draw it out so that the outbound heading is 270, the inbound is 90, the small area is 20 and the wedge is 130, with a line straight through from 20 to 130. If you are on a present heading of 360, hold the Post-it up to the HI so that the 90 degree number is aligned with 090 on the heading indicator. Now here is a great trick for even greater SA, look at the heading you are coming from and see where it falls within the numbers on the Post-it. In the example I gave, you are if you are heading 360 then that means you are "coming from" 180, which is to the left of the 130 heading written on the pad which translates into a direct entry. I know it sounds complicated but once you master it, it will take 20 seconds to draw it and 5 seconds to hold it up to the HI and get oriented.
Now, once in the hold, simply turn the Post-it with every turn you make (it can be on your lap) and it will give you an instant orientation as to where you are in the hold.
Other tips which were mentioned. If you have a decent GPS, use the OBS mode and set it to the inbound heading. This will draw an inbound magenta line through the fix and it works wonders. Also, an air traffic controller friend of mine told me early on that they could care less how you enter the hold, just as long as you stay in the protected area and are at the assigned altitude.
When in doubt whether it's a parallel entry or teardrop, just keep in mind that a teardrop is preferable because it's going to give you more time on the inbound segment because you will be further out when you make that final turn inbound. Parallel turns have a way of eating up space and by the time you're inbound you may be close to the fix.