I climbed it by taking the Herman Gulch trail (I-70 Exit 218 parking lot) around to the NE side and then going up what appeared to be an avalanche chute to the saddle between the main summit and the secondary summit (12,438'). This was a pretty steep ascent (45-55 degrees in places), partially through some very loose scree, but not all that difficult. There are no trails to the summit and it appears very few people climb it.
I went North to the secondary summit first, then took a break behind a large boulder to get out of the very high wind and eat some lunch. Then I went back down to the saddle and up to the main summit. By the way, what appears to be the summit one sees from I-70 is not the main summit which is around 100 yards or so to the North. There is a pole sticking out of a rock cairn at the main summit with a register that I signed. Because of the high winds on the summit and approaching bad weather signs I did not spend a lot of time reviewing the register, but I did not see a lot of signers for this summer.
I had the whole mountain to myself as there were no other climbers on it. One of the nice things about climbing a mountain that is not a 14'er, I guess. There were great views of surrounding mountains, I-70 far below and the Loveland ski area. I was on the main summit around 1:30 p.m. and the weather, besides being very windy, looked nasty back to the Northwest, so I did not stay long. I decided to try to go down the SE ridge, but I would not recommend it. Lots of loose rock and scree and pretty steep in places. On the way down it rained and even sleeted some, but by the time I reached tree line it was sunny again. I bushwhacked down a steep slope through the trees until I finally reached the stream, crossed it and was back on the Herman Gulch trail and back to my Jeep around 3:00 p.m. or so. I guess I did the round trip in around 5 - 5 1/2 hours, but I stopped to eat twice on the way up and I went to both summits.
I have read a couple of other reports on climbing Mount Bethel and I believe both of the other climbers went up the avalanche chute on the South side then went either East to reach the SE ridge or West to ascend past the snow fences. Either way would make the trip shorter than the route I took.