One of the things you have to tackle if you do a fantasy europe game is magic. It's understood in FE that magic exists and is out there. Ordinary people know the old pagan herbalist can put a curse on you, and that a truly pious man can call for a miracle, but in your day to day life, this fades in with general superstition.
What you won't see is generally the sort of overt magic that you'd find in most D&D campaigns. Slinging balls of flame is the work of the dark powers no doubt. So the DM must decide how he will handle spell casting in the campaign, from a rules perspective.
The simplest option is to let the players play what they like. If there's a magic user or cleric in the party, they function as normal. However, it's unlikely that they'll ever encounter many other magic users in the game world, and if they do, it should be a memorable occasion.
The DM should bear in mind that overt displays of magic will attract a lot of attention. Uprisings, religious sects and crusades have started over less, and a mob of villagers can make life hard for a suspected devil worshipper.
The DM may elect to limit spell selection to suitable spells. Clerics could get slightly more leeway here, as people are fairly ready to accept various type of miracle from a truly holy man, but most spells then would be information and observation type of spells. This can lead to a very "covert" feel, where the magic user somehow always happens to have an idea what is going on.
The DM may delay spell casting. For example, counting all casters at a 2 level penalty. Hence, a magic user does not actually get any spells until level 3 (at which point he gets the spells of a first level magic user) though he'd be level 3 for combat, saving throw and hit point purposes. This will help limit magic ability in most campaigns, though with so little magic out there, even this delayed spell casting will still be significant.
Lastly, the DM may simply not permit player spell casters, keeping magic in the realm of the NPC. In this case, the question occurs of what classes the characters CAN play. It may be advisable to bring in additional non-magic using classes to the campaign world, or use a system that omits classes altogether. Luckily, we will be providing just such an option in the near future. Stay tuned.
Thoughts are very welcome on how you will handle magic in Fantasy Europe. Likewise, if you want to write Fantasy Europe articles, let me know, and I'll make room for you on the blog