rent a car. If you still attempt those miles make sure they are all downhill with a tailwind. On a serious note there are 20 important things to remember but here are a few.Clothing,your shorts are going to rub things that are not currently being rubbed,those things can and will get raw and irritated(if not infected) have clean shorts and bag balm or some other ointment.Condition your guts for on bike diet, if your start getting "loose" your cheeks and B-hole are going to make it feel like your sitting on barbed wire for a 125 miles a day. You are going to need to drink water and "liquid food" all day. Don't plan to buy candy from from a little country store or eat the best things available, You need to have your food and drink to be a known source.150 a day,less sleep,and new food will make things a disaster.Don't ride at night, you can fall asleep while riding,really and when you wake up from the G force your direction is the pavement. Big Jim Elliott from San Diego used to ride his bike from SD to Yuma(190 each way w lots of big,nasty climbs and headwinds) and back without sleep training for a 24hr record you may want to try and find his email. If you don't have a sagwagon you should bring lots of cash and credit cards so when your backside and spirit break you can get a ride to a hotel.*if you posted this in MTB on purpose and you are doing all of the above off road,bring a GPS and a map so the rangers can find you and your bike. Bring matches or a flint for a signal fire. Make sure you film all this so Blair Witch Bicycle Project can be viewed by all of us.