I've done morning glories quite a few times. They cause, for me, severe vasconstriction, which means your veins shrink in diameter. It causes cramps in areas with large veins, your thighs in particular. It may not affect you thias way, but the effect is common. So, be prepared for it to be uncomfortable. I'd recommend not moving around much. Some people take yohimbe, or gingko biloboa to counteract this vascoconstriction, as these herbs a vasodilators. I'm no MD, so I'm not sure of the level of safety in doing this, but I know others have lived to tell the tail. EDIT: Also be aware that taking Vasodilators will make your veins shrink even more once they wear off than they would have otherwise. Word is that yohimbe is a particularly good pair because its slight MAO inhibiting properties. However, I believe the actives in MG seeds are LAA's or Lysergic acid amides, not amines, so technically MAO (monoamine oxidase) should have no effect on them.
The best way I've found, they way that always produces a psychedelic experience, is by grinding about 300 to 400 seeds up very fine, like sand, in a coffee grinder. Put them in a glass of distilled water (very important) and squeeze a good bit of lemon in. Wrap the container in aluminum foil so light wont get to it. Let sit for at least 24 hours in the fridge, shaking occasionally. Strain through a tee shirt. Drink the LAAmonade. This will most deffinately give you vascoconstriction though, be aware.
With this method I think what really happens is that you just trip off of the fine grains that made it through the filter. I've tried this same method but using cotton balls instead of a teeshirt to filter, and spent hours filtering it. I didnt feel any effects, except for nausea for about an hour.
They will also make you very nautious, but a lingering type, not like ayahuasca.
Personally I dont even bother with them anymore. I've learned some great lessons though. You probably wont have visions until after about 5 or 6 hours after eating them, but they can last easily up to 12 hrs. Effects begin about 1 or 2 hours after ingesting.
I dont use them because of the vascoconstriction. They make you feel generally like crap, but usually after 4 hrs the symptoms arent so strong.
Other methods are available to further purify them, but they rarely seem to be successful. I think MGs are psychedelic because of a synergy of different compounds, and purifying them makes them lose this. Also, LAA's are very unstable, and sensitive to light and heat, so they quickly degrade during the extraction process.
My personal opinion: Plant them and enjoy the flowers and get yourself some ayahuasca instead.
Maybe they're ok a couple times, but I think they are an inferior psychedelic plant. I dont use them because I think continued usage will lead to negative health effects. If you have high blood pressure, I would avoid at all cost. Just my 2 cents.
Sorry for the long post but these seeds kinda freak me out. I think they are a fairly high potential health hazard.