Hi Susie,
On the ET-312 my favorite routine is definitely Intense. It sounds like we use it in much the same way too. I usually tweak the MA knob back and forth between 1 & 3 o'clock, that subtle change really gets me going. I also like Orgasm (when I'm patient enough), Toggle, Stroke and Rhythm2.
Rhythm2 is great because its a constant power unlike Rhythm that slowly ramps up then resets. That's a custom routine you can load on the 312 via the eroslink software. There is a custom EMS routine and Stroke2 that are pretty neat too. Do you have Eroslink?
Another thing you should absolutely be trying is the audio input of your ET-312. Using audio files opens up a whole new level of stim because you can experience very complicated and varying routines without having to fiddle with the controls. The audio file input can add endless variety and make the machine even more hands free if you want to just surrender to a stim session.
On the electrode front, I've used tens pads and they are okay. The main problem is keeping them in place on the male anatomy. They are always coming off which is annoying. I know some people use hurt free tape to secure them though. What works best for me is hollow conductive rubber tubing with 2mm lead free solder as a core. The solder helps the tubing keep a shape which is nice. I usually have two loops around the base of the shaft as one pole with a head trode. The head electrode is a ring that sits just behind the glans on the corona with a half hoop that runs over the frenulum and urethra. This is very effective for me when it comes to hands free orgasms. I haven't had the chance to try/make any bipolar insertables but thats on the list.
When it comes to female setups, the tens pad route on either side of the clit is popular. A lot of women like the bi-polar electrode called the periform for vaginal stimulation. That electrode was designed for Kegel/Pelvic Floor exercises so its a good design. The other arrangement that works great is a combination of one pole on a vaginal electrode and a DIY conductive rubber "clit clip". The clip is basically like a bobby pin covered in conductive rubber that you pull the clitoral shaft through. Other arrangements that achieve the same effect are two short tubes of conductive rubber with elastics running through them and worn like a G-string. The net result of this is that current is passed through the nerve center of the clitoris down through the g-spot & vaginal wall resulting in some intense sensations. You basically hit all the good spots with that setup.
I've purchased all of my conductive rubber through www.happystim-usa.com. I'm not affiliated with them, but the owner has been very good to the e-stim community through the years. Its a great place to buy from despite the somewhat archaic site design.
I hope that helps answer some of your questions. How long have you been a 312 user?