When you first begin, look for trees and begin punching them. A good idea is to leave the bottom stump, jump on it and then punch upward to get the most from the tree without having to use steps, and then remove the stump. After gathering a few stumps, make some wood planks and a crafting table.
Having a crafting table, you should begin creating more wooden planks and a few sticks. Use these to create wooden axes, a sword, and a few pick axes. Continue gathering wood and making wood planks, you will need these to create a makeshift house before the first nightfall.
Mine some stone (grey blocks) so you can create a furnace. This furnace can be used to create some charcoal, so you can make some torches to light the inside of your house. Ensure that your house is fully enclosed and you have a few torches inside and maybe even outside to keep enemies from spawning so close.
Create a door for your house so you can easily enter and leave your house at will. If you choose to build inside the earth, then construction of your home will be easier than an above ground house.
Having a fully enclosed house with a door, torches inside and out, with a furnace and crafting table inside will be good enough to begin your first night. Once night falls you will encounter creepers, spiders, zombies, and skeletons. Creepers are the most dangerous, because they will explode and damage any terrain in the explosion (except for highly resistant material, which you won’t have access to this early on.
On your second day, you should begin gathering meat by slaying cows, chickens, or pigs. You should also begin constructing a farm nearby too. For this you will need a wooden hoe and a nearby water source. using natural earth you can till near the water to create a small farm. start attacking grass to gather seeds you can plant on these tilled and watered farm grounds. It will take some time for wheat to grow, so be patient. After the wheat is fully grown you can create bread out of it.
If you are lucky to find brown and red mushrooms about, you can create a bowl out of wood, and make yourself some mushroom stew to stave off your hunger bar for a bit.
Finding sugar cane about is another good quick farming option to create sugar and paper for ingredients.
After you have a farm or two with seeds planted, you should create some chests to store your items inside your house. have two chests together to create a big chest, which contains greater storage space. If daylight is still in your favor, you should gather more wood and cobblestone, so you can create better tools, and perhaps expand your house further.
Once you have more wooden material, you should create more sticks so you can build a fence around your farm. Animals can trample upon your farm and destroy them, so its a good idea to create an enclosure around it, and fences is usually a good idea. Once you have an fence enclosure and a gate to enter and leave, place torches on top of the fence for good lighting.
On your third day, you should be self-sufficient for the most part, so you should now be able to explore and discover your world. If you find iron, you will need a stone or better pick axe to mine it. Once you have gathered enough iron, and usually coal is find in close proximity too, so eyes open! Place your iron in the furnace to get iron ingots, and if there is sheep around, make a shearing tool! This shearing tool will let you gather wool from sheep so you can create a bed. This bed will allow you to sleep at night and set a spawn point, in case you get killed out there.