Speaking from experience - dealt with a painful fissure for several years. I wish someone had told me all these things early on, so that I didn't build up so much scar tissue along with a stubborn fissure, that surgery was the only choice for me. So here's my advice:
Do - wash backside with water and dab until clean every time you poo. (Portable shower spray bidets are under $20 on Amazon or eBay) - take a stool softener. Magnesium citrate and oxide worked best for me. - use a stool or box to put your feet on when pooing, makes everything easier when pooing with knees higher - take sitz baths - helps improve blood flow - add to your diet: brown rice, pears, flax seeds, apples, kiwis, figs, prunes, berries. Coffee first thing in the morning really helped me too. - light exercise, walking is best. - be patient and take doctor's advice. The prescription creams can take upto 4-6 weeks to work
Don't - eat white flour foods (or any other foods that constipate you) - go overboard with fibre and water. Fibre can increase bulk and make constipation worse. Too much water causes loss of electrolytes. Loss of electrolytes causes constipation. - take laxatives. Laxatives are only for temporary use. You don't want your body to rely on them as it can cause more health problems. - wipe with dry tissue. Wiping can aggravate the fissure and open it more - sit down for long periods of time
If your fissure hasn't healed from diet and care within 4-6 weeks, then if you haven't already, you should see a doctor before it gets worse. If the fissure is shallow and short, creams or botox will be enough to cure you. If your fissure is deep and/or long then ask for LIS.
LIS is the number one choice as it has a 95% success rate. Just make sure you have a good experienced CRS to do it. I had to have a second LIS months after my first because the first CRS I had didn't cut enough muscle.
Hope this helps!