when i soldered a lot, i used a hotter iron, but i was in practice, and could solder small stuff rather quickly. if your iron is not hot enough, you will have to hold it on longer, and the heat will eventually travel further, and possibly cause damage....by the same token, if you iron is too hot, the damage is obvious...
as for tinning, i used to heat the soldering iron, and then i'd melt some fresh solder on it, and then wipe it gently on a wet sponge. the solder should tin the tip nicely.
i also suggest using thin solder for these circuit board jobs, and even for soldering small guage wires, as the thin solder melts easier, and flows nicely, especially if you are using the common lower powered irons....15-30 watts.
also, if there is moving air, or cold temps in the room where you are doing this, it will definately hamper a good solder job. we used to also clean the circuit board's contacts with acetone, and then alcohol before we soldered to clean the area, and after the job was done, we would follow up with acetone again to remove the flux that might be left behind....this was because we had some issues with some boards after a year or so, and the problems were related to corrosion at the fixed solder areas where old flux was not removed after repairs were done.
another common problem i see is when the solder doesn't want to flow onto the wire, many folks have a tendency to melt the solder with the iron, and let it drip onto the solder joint, or connected wires, which can cover a spot with solder, but will not bond at all. avoid this as much as possible.
when i connect 2 wires, i like to fan out the strands, and then kinda mash them together with the other wire to be soldered, and then i twist them up, and they ment nicely..........i slide a small piece of heat shrink tubing on one wire beforehand, and after i solder the 2 wires that have been meshed together, i slide the tubing over it, and heat it up til it shrinks and forms to the connection.
one more tip, i usually use the flat side of the tip to heat the wire to be soldered, and it seems to melt and flow the solder into the wire, and to the iron. many folks use only the very tip, and that's fine if it's a tiny spot you plan to solder, but for wires, i use one of the flat sides of the iron tip.
these all seem like small factors, but collectively, they can make a solder job go right, or go wrong....
hope this helped...