HI C.,
I just finished training my 34 month old twins (boy/girl). Here's my advice.
Wait until they are ready.
I know you've heard it before and it sounds terrible when you feel like they should be trained already, but the truth is, as long as they are introduced to it, it will happen when they're ready. For example. I used the potty training boot camp method. First we tried at 30 months. I stayed home for two days straight and cleaned up accident after accident. They simply weren't ready. Then at 33 months we did the same thing. Again, accident after accident and they weren't ready.
We started a bedtime ritual at that point. We let them "practice" on the potty just before bath time. That was the only time we asked them to sit on the potty (I have the baby bjorn potty seat on the big potty, training twins was hard enough, I wasn't going to train them on tiny baby potties and then re-train them for big potties!) That's why I wanted to get a potty seat and not a potty chair. Anyway, we asked them to sit on the potty before bath time. My son picked up on it very quickly and usually peed right away. We rejoyced and sang and danced. But it was a no go for my daughter. She liked to sit on the potty but nothing happened. That's OK!
Doing this once every night with no pressure or even mention on the potty during the day helped us. The twins were less stressed out and so were mom and dad. Then at 34 months I decided to try it again. (about six weeks after this "bath time" potty practice ritual began) I bought construction paper and made some potty charts. I bought a couple sheets of tiny stickers (smiley faces and stars) and I let them know when they peed on the potty they got one sticker for their chart. So I buckled down one thursday in July (the twins were 34.5 months old) and we just wore underwear and t-shirts. I think this step was important because they didn't have a lot of clothing to get in the way and they were easily reminded it was potty day! I sat them on the potty every 30 minutes. I had two timers, one for my son, one for my daughter. I actually set my son's on the hour (say 9AM, 9:30AM etc) and set my daughter's on the quarter hour (say 9:15AM, 9:45AM) So personally, I WAS IN THE BATHROOM ALL DAY! I shelved all responsibility for about 4 days. By the second day I was able to see their queues and the timer wasn't needed. I just put them on the potty when they showed signs of needing to go. They LOVED the sticker method too. Finally! Something they were (and still are) excited about.
I guess my point it, wait until they are ready. If you do the boot camp method like I did, and it doesn't work after a day or two (large commitment, I know!) shelve it all together and start again in another month. That's what I did, and they were finally ready on the third try.
OH, and my favorite carpet cleaner is this white bottle at Target (and other places I'm sure) called Folex. No mixing or setting etc. It's awesome stuff!
Hang in there. It's frustrating but eventually they will get it. Oh, and we did a lot of reading on the potty. Book after book after book. My son took to peeing right away. When he had to go, he had to go. But my daughter would get the urge to pee, but then stage fright. So I spent many a hour in the bathroom reading library books. Patience is key. There is such a great feeling of accomplishment when they do get it. So keep trying every month or so. Hang in there!