I'm level 42 right now. I put in the hacker and lockpicking perks right away because it always pays off. There are a ton of computers and locked rooms that carry useful stuff. I could open pretty much any safe and security door in the game within the first few hours so I've never run out of ammo for anything... except that damn railway rifle.
I got the science, demolition and blacksmith perks early on too so I could make grenades and radaways and weapon mods. I focused a lot on strength, intelligence, charisma and endurance on the early levels too. I found the armor bench pretty useless though. I used Kellogg's outfit for a long time instead because it was stronger than anything I could make. Now I'm using the Silver Shroud costume.
A good tip to level up is to cook a lot of food. It earns you a decent amount of xp, and it's pretty useful too. It's a nice change from the cooking system in Skyrim. Cooked food is the best way to regain health during combat too. It fills up the health bar as soon as you eat it, whereas the stimpak has that syringe animation. If you're getting attacked by a melee enemy you're toast before the character has even managed to get the needle into the arm.
