Hi, I posted pretty much the exact same topic a few weeks ago:
http://jetcareers.com/ubbthreads/showflat.php?Cat=&Board=UBB1&Number=65608&Forum=All_Forums&Words=cessna%20pilot&Match=Entire%20Phrase&Searchpage=0&Limit=25&Old=3weeks&Main=65512&Search=true#Post65608
Since I posted that, I'm up to 16.3 hours dual logged in the seneca and have done about 23 landings in it. I'm also using a PA34-200 (although a 1972 model) and it took me about 10 landings before I could land it without any instructor input.
Now I can do respectable short field landings and almost consitently grease regular landings. It just takes practice to be honest. Like you, I had flown nothing but high wing cessna singles before I started flying the seneca on the first of this month.
Like I said, in the beginning, I was having a lot of trouble controlling the seneca on landings. To remedy this, on my 6th multi lesson, my CFI told me we were going to practice nothing but landings till I got them down cold. I did 6 landings total that day, and since then it's been like night and day. Single Engine Landings are no big deal either, once you get the multi-landings down.
To land the seneca from a traffic pattern I use full flaps (40 degrees) and maintain blue line (105 mph) until landing is assured (usually around 300 AGL or so on final). At this point, I will slow the airplane to 95 mph, or 90 mph for a short feld. Then, you just keep flying into the runway, nose down, and flare at the last possible second, right before you think you're about to plow the nose wheel into the pavement. Even then, don't "pitch up". Bring the nose up *JUST* enough so that the mains will touch first. You should not touch down much slower than your 95 mph approach speed. On instrument approaches I configure the airplane for landing before the final approach fix, holding 115 mph on the glideslope with flaps 25. I typically vacate blue line at 300 AGL on non-precision approachs and decision height (only if visual contact is made) on precision approaches.
If you try to flare the nose too high, you will float back up and plop back down. In addition, the wings will start to drop. This is why it's so important to fly the airplane onto the runway at close to the approach speed. Holding airspeed Into the ground is the main trick you have to master for good landings in the seneca. You don't want to hear the stall warning horn go off during the landing like you would in a cessna.....the seneca gets too unstable when you get that close to stall (wings will drop and you'll start see-sawing, especially if any crosswind at all exists). Trim can help......but I usually don't need any additional trim to slow from 105 (blue line) to 95. I don't like taking my right hand off the throttle and reaching down to turn the trim wheel at this critical stage of flight. You'll be pulling back on the yoke with a decent amount of pressure, but it's nothing that any adult shouldn't be able to handle.
Since you're in canada, your airspeed indicator is proabably in knots or kmh, so the speeds may not apply unless you do some conversions, but the basic technique should be the same.