If you are starting from scratch, give it a 4-6 month training window. Go ahead and find a tried and true schedule and post it on your wall. I used Hal Higdon’s 16 week intermediate marathon training schedule. Let yourself stray from the schedule based on your instincts. Everyone has their own personal challenges which will impact daily life. Just know that if you keep running, your legs will get stronger. 10% increases in mileage per week is considered the gold standard. Many runners alternate weeks increasing their sunday long runs to new distances, then falling back to rest the legs. I started out running totals of 15-20 miles a week, then worked my way up to 50-60 miles (with a 20 mile longest sunday run) in 12 weeks, then used the last 4 weeks to taper back down to 20-30 range, letting the legs recover before the big one. Cross-training is essential. I chose cycling and hiking. If I felt I needed a day off, I took it. If I could run 5 days straight, I did. The back-2-back concept is very helpful for learning/feeling how to run on tired legs. Hitting a wall here and there is good for you to experience the pain and try and run through it. Psychological/mental conditioning.
There is such a thing as over-training and it’s dangerous! Keep to the schedule if you can. You could injure yourself. New runners can be prone to injuries because your body is still adjusting to the high impact sport of long distance running. What happens with a new runner is your body tries to acclimate to the stress of impact, and often expends energy trying to stabilize/protect your legs. Experienced runners will find that, once acclimated, the body will be able to use those energy channels towards forward momentum.
Buy quality running shoes that are made for long distances. My personal favorite shoe and the one that got me through: Brooks’ Launch 3! A ‘neutral trainer’ that is very supportive but not too heavy, and has the kind of midsole cushioning which pushes back to help your forward momentum. Be aware of ‘pronation’ and have someone check your stride. Shoes wear out in 300-500 miles. Have an alternate pair and keep track. Faster runners tend to run on different shoes than they train on. Hokas are cushiony and good for recovery runs. The Pegasus 33 Nikes are good but a bit heavy. There are tons of useful shoe and product reviews all over the internet. Use them.
Use anti-chafing sticks like ‘Body Glide’ for surfers. Long runs will rub raw your arms, feet, inside of your thighs, anywhere there’s friction. Experiment with socks. They do make socks these days which prevent blisters, but moleskin helps, too. I experienced a knee injury while breaking in my Hokas which caused me to need new shoes only days before my race, and the ‘Swiftwick’ socks I was offered kept the blisters at bay. If you do get blisters while training, there are safe ways to pop and bandage them and keep running without delay. Don’t forget suntan lotion if you are fair-skinned. Nobody loves skin cancer and you may be out running for 3-4 hours at a time…