Getting to the beginning of the trail is not easy unless you go there by your own car.
By car: After you get to Ust-Barguzin, you should pass the bridge over Barguzin River, and turn left (almost backwards) at the first crossroads. In 5-10 minutes you will reach the National Park. From the checkpoint of the national park there is a dirt road. This is the only road, so there is no chance you can miss it. Just before the mountains, there is a turn left. Take it, and in 1.5 km you'll see an information sign at the beginning of the trail.
Depending on your driving skills and condition of the road, the way to the campsite will take you from 40 minutes to 1.5 hours. We advice you to camp before reaching the beginning of the trail because there is a big chance that you will be unable to drive further because of your car's clearance. But if you own a SUV, it's not a problem, unless it was raining before. There are many camping places on the shore of Lake Baikal with a great view on the Svyatoy Nos peninsula. From there you can get to the beginning of the trail by car in 15-20 minutes. Or you can just park the car a bit closer and then go to the trail by foot. It will save you some time.
By public transport:
First, you need to get to Ust-Barguzin. The only way to do it that does not cost you a lot is by taking a bus from Ulan-Ude. The schedule can change every year, there is almost no source of up-to-date information. The only thing you can do is calling the ticket office. They speak only Russian, so you will probably have to ask someone (for example the receprionist at your hostel) to call them and ask for the schedule and book the tickets. In summer the buses can be overbooked, so do it in advance. The website of the bus station is: http://avtovokzal03.ru/contact-us.html
From Ust-Barguzin there are several ways to get to the beginning of the trail. First is to take a taxi directly to Svyatiy Nos cape. It's the most expensive, but also most comfortable way to get there. The cost will depend on the driver and your trading skills. Second way is to take a taxi to the beginning of National Park and then go by foot (25-30 km) or try to hitchike. It is the cheapest option, and there are usually no problems with finding a ride, as there are lost of people driving to the coast to camp