Where/how can I find a local/professional guide that will take me safely up Mount Kilimanjaro and Mount Elbrus?
For Mount Kilimanjaro you have to book your trip through a Kilimanjaro trekking agency/climb operator that has been approved by the Kilimanjaro park authorities.
You can book with a travel company that is licensed to run tours but these will often be a little more expensive. For a cheaper option when you get there ask around. You can find many local guides that'll take you up.
I haven't climbed Mount Elbrus but I would assume the same applies (ask around once you get there).
I just got back from climbing Kilimanjaro, and we went through Focus in Africa
The guy who organized our trek, Nelson, was very accomodating, and helped us arrange hotels and a safari after our climb as well. We did the 7 day Machame route, and it cost $1550 a person for a group climb. If you want to do it privately it's $200 extra. You can do Machame in 6 days, but the 7th day is very helpful for getting used to the altitude. It greatly increases your chances of making it to the top.
Focus in Africa was great for a lot of reasons. First of all, all their profits go to benefit an orphanage in Arusha, and it's nice to know your money goes to a good cause. Second, they don't directly employ porters/guides, but contract out, and the tips they recommend giving them are higher than the porters/guides usually get. It's still really cheap (only $30 for each porter for the entire time, for example), but the porters were very happy with their extra money.
I have recently done a lot of research in to guides for doing Mt. Kilimanjaro here are some points I found that were important.
There are three types of tour groups low end, middle and high end. In 2011 the price for low end was roughly 1800 - 2100USD middle is 2100 - 3000USD and high end is anywhere from 3000 - 5000USD.
You'll find that the high end groups usually do not do much more than the mid range groups to justify the cost.
I would also not reccommend using a low end group as corners are cut especially when regarding safety.
One of the main things to consider is how long the trek up is. If it is 6 or less days then your chances of making it to the top are greatly reduced, it is somewhere in the vicinity of 60%. For each extra day you add for acclimatization to the altitude you improve this 60% chance by roughly 10 - 15%. However this is subject to how well you adjust to the altitude which is completely random.
Another point to consider is how well the porters are treated by their guides/the tour operator. Look out for an operators that is a member of the 'Kilimanjaro Porter Assistance Project' In this way you have some assurance the porters are treated well and paid accordingly for their work.
I climbed Kilimanjaro a couple of weeks ago, and booked it with Gap Adventures. It costs €1139 per person.
Gap Adventures uses the local operator Zara Tours for this trek, and it was a great experience. At first I was a little worried since the 5-day Marangu route supposedly has a high failure rate due to the quick ascent, but in a group of 13 people everyone made it to the crater rim (Gilman's Point), and 12 of us made it to the very top (Uhuru Peak). The one who didn't make it to the top gave up on his own (it's pretty exhausting), but he could probably have made if he wanted to.
I have used Gap Adventures for this trip and a safari, and can highly recommend them.