People start dying of starvation on day 4. That means you need to get food production going as soon as possible. This will walk you through what you need to do to survive to day 5 on a normal map as of version .45.
Step 1 Scouting! As soon as the new map loads, you need to pause the game, default key space. Then, you should figure out where the hostiles are on the map. Most of the Froggies are going to spawn in or around the patch of Jungle on your map, which you can easily see on your minimap as a patch of brighter green. If the Jungle is on the far side of the river, then your people are safe. If not, then you need to be very careful about giving the next command.
Step 2 Gathering! As soon as you've figured out where the hostiles are, you need to tell your people to harvest (bottom commands menu, far left) two things, Fruit and Wild Wheat. You have two options for that. While the game is still paused, you can highlight all the Fruit Trees and Wild Wheat you want harvested while avoiding flowers. You could also just highlight a massive area to harvest, allowing your people to gather flowers along with the food. The first option saves time for the Townies, the second option saves you some clicking. Both usually work.
Step 2.5 Dead Guys! Once you have the harvest order out, you can unpause the game and let the Townies run off and do their thing. If you did it right, the Townies will avoid all the Froggies and come home safely. If you did it wrong, you'll lose some guys on your first day. If you did it wrong and you hear one of your people die, you need to pause the game and then click on the notification at the top of the screen that says "someone dies". That will center your screen on the human corpse. If you do not pause the game immidiately, there may be other combat going on that will quickly cause the "somone dies" notification to scroll off the top of the message board and be lost. What you should do once the screen shows the corpse is to right click it and select "destroy".
If you do not pause the game in time and the message is lost, you can try to find the corpse by moving the screen around the map, sticking to in and around the Jungle area that the Froggy came from. If you cannot find the corpse, then you need to que up a Grave (decorations, outdoor) to be built. That will send a Towny out to pick up the corpse as soon as some stone is availible.
This whole bit about the corpse is important because it does two things. Firstly, it and the Stink Clouds it gives off count as Unpleasant Things which drive off immigrants. Secondly, it will eventually decompose into Human Remains which will spawn Ghosts of Heroes Past, a potentially dangerous monster.
Step 3 Farming! So, now we have a lot of Fruit and Wheat scattered around the map. The next step is to till some grass (4x4 should do for now) and plant the Wheat (using the menu on the right). The Townies will begin to run out to get the Wheat they just harvested, turn it into seeds, and then plant those seeds. If you managed to collect more than 16 Wheat in the Step 2, then till some more soil and get all the wheat in the ground. You'll be able to tell how much Wheat you have by pushing F2, selecting Food, then Harvest, then Plants. You'll see on the top left of that page a picture of Wheat, with a 0 on the left and right of it, and a number on the picture. The number on the right tells the Townies the minimum number of the item you want to have at all times, and the Townies will work to get that many. The number on the left is what you can adjust to tell the Townies that you want so much of a certain item, but to not produce any more after that. The middle number is how many of the item you have. Push the up arrow on the number to the left of the Wheat until it says 5. Your Townies will now harvest any Wheat from the field you tilled until there are 5.
You should try to have a farm that's about 7x7 to be on the safe side. As your guys harvest the Wheat, they will make seeds so they can continue planting as you instruct. Remember Townies have no initiative and need to be told to do everything.
Step 3.5 Storage! Remember that fruit? It's scattered across the map. You should create a stockpile near the farm for prepared food using the commands menu on the bottom. When your Townies have some time, they'll run around collecting the fruit. If your guys get hungry, they'll grab a piece and have a snack. It isn't very filling, though, and natural Fruit Trees do not grow their fruit back. However, it'll ward off starvation for a little while.
Step 4 Chopping! Now time to collect some wood. Find an area that you think contains about 30 trees and tell your Townies to chop it with a button from the bottom commands menu. As they do so, set up a Carpentry zone using the commands menu and then place a Carpenter's Worktable on it using the left menu, Utilities. A Towny will make a Worktable out of a log and drag it over. Be sure the area you chose to log didn't have Froggies!
Step 5 Mining! You need to find an area near your town that's grey. That's Stone, and it indicates that just below is one of the most important resources in the game. You need to dig a hole (commands menu) on the Stone and place a Ladder (utilities) in it. At the same time, you should make a Bakery zone (commands) near the farm and place a few Baker's Tables in it (utilities). Once a Ladder has been placed on the hole, use the mouse wheel or X to go down a level. Use the commands menu to tell your Townies to mine out a bit around the ladder, about 5x5 should do.
Step 6 Utilities! Now It's all about building things. Go back to your Carpentry zone and build a Wood Detailer (utilities) use F2 and click Utilities. Click up on the number to the right of the Stone Hammer to tell your Townies to make one. At the same time, you should tell your guys to build up to 3 Mills near the Farm. Finally, you should use commands to make a Masonry zone and place a Mason's Workbench(utilities) in it.
Step 7 Baking! By this point, you're probably on day 3. Your guys are slowing down from hunger, and their "no bread" emotes should be flashing.Don't worry, the end is in sight! All you need to do is build a few Baker's Ovens and use F2 (Food, Baking) to set a minimum 5 Bread. Your mills should already be pumping out flour, and once the first Oven is set up, they will begin baking.
Step 8: FOOOOOOD! It's time to breathe a sigh of relief as the sweet "om noms" of bread being eaten are heard. Congratulations, you've saved your defenseless Townies from a horrible death by starvation.