As said before, the first thing to do with a new iron is melt plenty of solder on the tip the first time you plug it in. That's "tinning the tip". Some Weller irons used to have a large copper tip with a tinned coating. If you had one of those you could file the oxidation off, get back to bare copper, and tin the tip again. But most often, you can't file tips and must replace them. Wherever you bought the old iron has new tips (last time I bought a Weller was a home improvement store, and they had a package of replacement tips). Forget lead-free solder, you want 60/40 as mentioned earlier. Lead-free needs more flux, more heat, and is more hassle if you don't need to meet RoHS regulations. If you get flux, get a liquid type. There are flux pens. At one place I worked, we had liquid flux in a small bottle with a needle-tip on the end. Very handy!