Welcome to the club. I'll add my $.02 to the already good suggestions.
1) Open Houses: Start doing open houses right away. Pick an area you want to work, then find someone in your office who has a listing in that area. Ask them if you can do an open house for them. More often than not they will say yes unless the owner objects. Make sure to put your open house on the MLS. Then post on Craiglist, Backpage, etc. Print up a minimum of 50 open house flyers. 1 to 2 days before the open house go and knock on doors in the neighborhood. Give a flyer ONLY to people who answer the door as your goal is to talk to people, not to get them to your open house. If they actually come, that's a bonus. When you talk to them tell them you're having an open house Sunday 1-3 (or whenever it is) and ask them if they have any family or friends that may be interested in moving to the area. They'll probably say no. Tell them if they think of any to please let them know about the open house. Thank them and start to turn away. Then turn back to them and say, "you know, we'll be generating a lot of traffic at this open house and it won't be a fit for everyone. Obviously the buyers coming are interested in moving to this area. Do you know of anyone else in the neighborhood thinking of selling their house?" Some times that person has been thinking of selling. Most will say no but you will find some who will tell you about a neighbor who wants or needs to move for some reason. Write down all the information they tell you. When you get to that persons house tell them one of their neighbors told you they may want to move and you'd like to talk to them about that. The real purpose of the open house isn't to sell the house you're holding open. The real purpose is to leverage it to try and find more business. My first buyer and first listing came from doing open houses when I was new.
Before the open house put out at least 15 directional open house signs with your name and number on them. Do lots of open houses in the same area and always put out the signs. People will start to recognize the signs with your name and think you're a player in the area.
At the open house talk with every guest and get as much information as you can. Ask them where they are in the home buying process. If they say they're just starting, ask them if they've been pre-approved with a lender yet. If they say no, have a list of 3 lenders you have a relationship with (establish a relationship with lenders) ready to give them and explain to them the benefits of being pre-approved. Now you've given them knowledge of the buying process and offered them something of value. Ask them how many properties they've "toured inside" so far? When they tell you, ask them if they've all been open houses. If they've all been open houses they probably haven't signed with an agent yet. Ask them how they're finding the houses they've looked at. Hopefully they don't say from their agent. Offer to set them up with their own customized search on the MLS that will email them houses that match their criteria as soon as they hit the market. Explain that this will give them an advantage over all the others using Realtor.com, Zillow, Trulia etc because those sites don't always have the most up to date information. Ask them for their email address and criteria so you can get them setup. Now you have a method of contact to follow up.
If you're broker provides you an app ask the buyers, "what kind of phone do you have?" When they tell you (and most will need to show you) say "Excellent. We have a fantastic app that you can use to help you in your search. I can send it to you right from my phone. What's your number?" Then stand there waiting until they give you the number. You just got their real number (people sometimes leave fake numbers on sign in sheets) and you now have a direct way to follow up. The app should also alert you when they search for properties and you can follow up with them about the properties they searched.
If your broker doesn't have an app find a lender that does. They can provide you with a co-branded app.
Get as much information as you can from each person that comes through your open house. Have a list of other similar properties for sale in the area. This demonstrates market knowledge.
Finally, if they don't have an agent, try to set a meeting ASAP after the open house. Invite them to your office, meet them at their house/apartment, Starbucks for coffee or wherever. Meet them and get them signed.
2) Expireds: Ask your broker if they provide any phone lists for expired listings. Some subscribe to a service. Get that list and call these people every day until you talk to them. Ask your broker for a good expired script. Memorize it and role play with someone. If your broker doesn't provide expired numbers look into subscribing to a service yourself or going in with another agent/s and subscribing. There are several out there; Landvoice, Vulcan7, RedX to name a few. Ask experienced agents their opinions on the various services.
3) FSBOs: FSBO numbers are easy to find. Getting the listing however is a pain. Most think they know everything and they don't need an agent. It takes time to work most FSBOs but it can be done. In fact some 80% of FSBOs end up listing with an agent. Roughly 10% actually sell on their own and the rest give up completely. You can find FSBO #s on Zillow, forsalebyowner.com, Craigslist, etc. Google for sale by owner and you'll find several sites with numbers.
These are the 3 methods I've found to be the most successful. More of my business has come from expireds than anything else. You can also work your sphere of influence, door knock neighborhoods you want to work. Whatever you choose to do get after it. Business will NOT come looking for you in the beginning. You have to find it.
One last thing. Don't be shy about hitting your broker up for advice, tools, scripts, etc. A good broker will want to help you succeed because the more business you do, the more money they make. If your broker isn't being supportive find a different broker.Hope this helps. Good luck!