Lead-free solder is fine to use, but you must use the right sort, tin/silver/copper, not tin/copper which is
basically just tin and not a eutectic at all (goes all pasty and won't remelt). And you don't get poisoned.
The right temperature iron is the most important thing - it must be hot enough to solder quickly (too cold
will cause heat damage, ironically!), and constant temperature. Keep soldering bits clean of oxide
(switch off when not in use, tin and clean the bit end often when in use)
Practice on scrap circuit boards. The easy/quick technique is hold the solder between the iron and the part so
it melts onto both simultaneously. Always always use rosin-cored.