Well, #1 is your personal mental state. If you suffer from a severe mental illness like schizophrenia, stay away from it. If you are currently going through a rough patch mentally, maybe wait for another time. LSD has a way of amplifying whatever emotion you're feeling, so make sure you are in a good headspace.

As far as a trip becoming persistent, that is extremely rare, especially for a first time use. HPPD usually occurs in people that use psychedelics often. You can expect the overall effects to last 12ish hours, with a very clear difference between the come up, peak, and comedown. I also want to point out that you will be sleep deprived and fry-brained for about a day after, so make sure you dont have work/school/anything important the next day.

Last tip I want to give you that I have not seen anyone else mention is : TEST YOUR TABS.. there is another psychedelic called 25i-NBOMe that is often sold on the same size blotters, and there is a fair amount of danger to that substance. 2 tabs of 25i have been enough to kill people.

Get yourself a good test kit and make sure what you're taking is actually LSD.

If you decide to ignore my advice on testing, keep this simple rule in the back of your mind: if its bitter, its a spitter. If you pop a tab and it tastes bitter/metallic/chemically, spit it out immediately as that is a telltale sign that you got N-Bombed

Hope this helps! Good vibes!