Summons also attack creatures if you attack them (This includes ranged attacks)
Polearms "can't reach far enough" exactly 50% of the time when reaching past a freindly.
The addition to the "sandwich" tactic described by crate, some other effective tactics for using summons are things like this:
(x is monster, S are summons @ is you)
Attacking X from this position gets you attacks from both your summons.
Drawing a monster towards you past one or more of your summons lets them get "free" attacks, polearms are helpful for setting this up.
You'd think this would be good, but summons generally aren't good tanks (with a couple exceptions in certain circumstances, learn what those are, by the way, ice beasts are poison-immune, and cold damage slows snakes for example) So it's uncommon that this actually a productive situation, even if you do have a polearm, usually you're better off with this:
or even this:
This allows both you and your summon(s) to attack x at the same time, while you tank.
Use position switching liberally, it's an excellent escape tactic and can reliably put a SPAAACE between you and a nasty melee critter.
The most important thing about being a summoner is "be able to kill stuff without your summons" treat them like extra melee damage, train your character like a melee character with some spell support, playing fragile races means that much more exp needs to go into defenses. One of my favorite summoner races is Dr (because of the free ranged attack and the bonus AC without spellcasting penalty) but there's lots of good races.