I hate this spell. I don't know how much clearer I can be than that. This spell allows a Player to "bend the rules" of reality and become whatever his imagination allows him to, within boundaries. The first time I had a player use this spell, I was caught by surprise and I let him do things that the spell simply wasn't capable of doing. Since that time, I have read extensively about the spell and have set guidelines about its use. The following text is how the Polymorph Self spell should have read in the Player's Handbook.
Level: Rgr 4, Sor/Wiz 4
Casting Time: 1 action
Duration: 1 hour/level (D)
Polymorph Self allows the caster to change into another form of creature. The caster may change form as often as desired for the duration of the spell simply by willing it so. Each change is a full round action. The new form can range in size from Diminutive (6 inches to 1 foot) to one size larger than the subject's normal form. Upon the initial transformation, you regain hit points as if having rested for a day (though this healing does not restore temporary ability damage and provide other benefits of resting for a day). If slain, you revert to your original form, although you remain quite dead.
You acquire the physical and natural abilities of the creature you have polymorphed into while retaining your own mind. Physical abilities include natural size and Strength, Dexterity, and Constitution scores. Natural abilities include armor, natural weapons (such as claws, bite, swoop and rake, and constriction; but not petrifaction, breath weapons, energy drain, energy effect, etc.), and similar gross physical qualities (presence or absence of wings, number of extremities, etc.). A body with extra limbs does not allow a character to make more attacks (or more advantageous two weapon attacks) than normal. Natural abilities also include mundane movement capabilities, such as walking, swimming, and flight with wings, but not magical flight and other magical forms of travel, such as blink, dimension door, phase door, plane shift, teleport, and teleport without error. Some creatures (such as dragons* and sprites) have flight speed listed but their lift is provided through magical means and therefore is not gained. Extremely high speeds for certain creatures are the result of magical ability, so they are not granted by this spell either. Other non magical abilities (such as an owl's low light vision) are considered natural abilities and are retained.
Any part of the body or piece of equipment that is separated from the whole reverts to its original form.
The caster's new scores and faculties are average ones for the race or species into which you have transformed. You cannot, for example, turn into a mighty weight lifter to give yourself great Strength.
You retain your Intelligence, Wisdom, and Charisma scores, level and class, hit points (despite any change in your constitution score), alignment, base attack bonus and base saves. (New Strength, Dexterity and Constitution scores may affect final attack and save bonuses.) You retain your own type (for example, "humanoid" and not "dragon"), extraordinary abilities, spells, and spell like abilities, but not your supernatural abilities. You may cast spells you have components for but you need human like hands for somatic gestures and a human like voice for verbal components. You do not gain spell like abilities of your new form. You also do not gain supernatural abilities (such as breath weapons and gaze attacks) or the extraordinary abilities of the new creature.
The new form can be disorienting. Any time you are in a stressful or demanding situation while polymorphed (such as combat or anything that would require a Concentration check of at least DC 15), you must succeed at a Will save (DC 19) or suffer a -2 penalty on all attack rolls, saves, skill checks, and ability checks until the situation passes. If you use the same form over a long period of time (36~48 hours a week over a years time), you may overcome some of these drawbacks (DM's discretion).
When the polymorph occurs, your equipment, if any, transforms to match the new form (although you cannot use this spell to gain equipment that you do not have such as a greatsword or rope). If the new form is a creature who does not use equipment (aberration, animal, beast, magical beast, dragon, elemental, ooze, some outsiders, plant, some shapechanges, or vermin), the equipment melds into the new form and becomes nonfunctional. Material components and focuses melded in this way cannot be used to cast spells. If the new form uses equipment (fey, giant, humanoid, some outsiders, many shapechanges), your equipment changes to match the new form and retains its properties. If in doubt about a new forms ability to use equipment, refer to its entry in the Monster Manual.
You can freely designate the new form's minor physical qualities (such as hair color, hair texture, and skin color) within the normal ranges for the creature of that type. The new form's significant physical qualities (such as height, weight, and gender) are also under your control, but must fall within the norms for the new form's species (no 7 foot Kobolds). You can change into a member of your own species or even into yourself. (If changed into yourself, you do not suffer the above mentioned penalties from the disorientation of a new form.)
You are effectively disguised as an average member of the new form's race. If you use this spell to create a disguise, you get a +10 bonus on your disguise check.
Incorporeal or gaseous forms cannot be assumed. You cannot take the form of undead or that of a construct. The form you take must be that of a living creature (polymorphing into a rock is not allowed).
* Dragons of a size larger than small begin losing their natural ability to keep airborne and their innate magic gives them lift. These dragons only have a small portion of their flight ability due to natural means and therefor cannot adequately fly without the magic. Polymorphing into a Large dragon to recon the area is not really viable but changing into a hawk or owl is a better choice.
Please note that this text is taken from the Polymorph Other text and altered to fit Polymorph Self. I have added examples where necessary. I encourage players to make index cards of frequently used forms to have as a reference instead of having to recalculate each time you use the spell.