It's pretty easy; just make sure you always get an H Scene before the day ends (there are 30 scenes, and a 30 day limit - so if you ever get to midnight without triggering an H Scene, reload).
For each girl, after you've captured them visit them in your basement to unlock the start of the next scene with them. You can manufacture items in your kitchen.
When walking around, going too near to an enemy will cause it to chase you. Most only do 10 damage, but since there are no invulnerability frames this can add up fast unless you immediately run away. If you get trapped in a corner by a few enemies, or in a one tile corridor (eg ladders), you're pretty much dead. Bears kill you in one hit, so avoid them.
Sparkly areas on each screen are either collectable items, or they'll refill your health. Examing them takes an hour. You need to get all the items, but you'll only pick them up after you know you need them (annoying...). Moving from screen to screen also takes time. As time progresses, it gets darker; at night, ghosts come out to chase you. At midnight you automatically go home (if this ever happens, you can't get the good end).
There are nine screens: your house is in the top left. South is a screen with ladders. South again to a lake. Middle top has a crocodile infested bog. Top right is the beach where people washed ashore. True middle has a grassy plain. Middle right is a forest. Bottom middle is a desert area. Bottom right is a rocky area.
(These are in left to right, top to bottom order in the basement)
1st girl: You catch her automatically.
(Remember, talk to each girl in the basement before starting their second scene). Visit the left side of the ladder area to find a monkey blocking an area. Head there at 6pm and the monkey is gone; enter the area. Then talk to the girl, and walk back with her to the area, again at 6pm.
2nd girl: Find her riding a horse in the top left of the grassy area. Head south to find a carrot; leave and return, then head to her again to set a trap with the carrot. Leave and return, then talk to her.
Find a larger carrot in the bottom right of the forest area, then talk to her.
3 girl: She appears in the ladder area after a certain point. Find her again in the right of the ladder area behind a tree to catch her.
Examine a spot in the swamp towards the top right (in the water). Return there with her.
4th girl: She'll appear on every map screen. I think you have to catch her once on each screen. Keep looking for her whilst doing other events. After catching her enough, she comes quietly.
Pick the rope up on the beach, then talk to her.
5th girl: You'll find her in the forest, but her cat gives her warning if you get close. Head to the ladder area and pick what I assume is catnip from the patch up the ladder on the far right, then return to her.
You can find the cat in the grassy area. Find a fish for it at the beach, off of one of the wooden piers. Take the fish to the cat, then bring the cat back to the girl.
6th girl: She's behind some bushes at the lake (bottom left), but you might have to catch her little sister (3rd girl) before you can get her.
You can find the elastic band in... I think it's the desert area. One of the sparkly patches.
7th girl: Find her in the ladder area, down the right one. Talk to her and she runs away. Examine the ladder she goes down, then the middle, to set a trap. Leave and come back, then talk to her.
Talk to the gorilla in the right of the forest. Collect a banana from the tree near your house, Talk to the gorilla again, then bring the girl to him.
8th girl: Find her in the middle of the grassy area. She runs away fast, but only in a straight line. Keep catching her, and eventually her shoes will fall off, and you can catch ger properly next time.
Talk to her twice in the basement (after meeting the stands on rocks girl), first to get her shoes, then to start the second scene. Just wait until the right day, then talk to her. I think a message will appear when you start the day when it's the right day. Or just keep checking.
9th girl: Find her in the rocky area, and she jumps on some rocks so you can't get to her without hurting your feet. Get the shoes off of girl 8, and you can now get her.
Find the wood to make the bed by examining a log in the forest. Find the animal fur by examining a skeleton in, I think, the desert. Make the bed in the kitchen, then talk to her.
10th girl: Find her by the lake. (Bottom right). She won't have sex with you in the day, though. Come back at night and sneak carefully after her without letting her see you. (Tricky to do this whilst avoiding ghosts and bees...) When she gets to the water, talk to her.
Go back to the lake and pick up her uniform from where she was washing.
11th girl: She's at the bottom right area of the desert. Talk to her, and watch as she beats up a lion. Whilst she's still tired from that, talk to her again.
You need to find two kinds of fruit. One is in the bottom right of the swamp, the other is I think to the right in the rocky area. Mix them, then talk to her.
12th girl: Find her being threatened by a wolf in the forest. Leave her there, and go and catch the speedy rabbit from the grassy area (appears to the right, lower down). Bring the rabbit back and save her.
Find the dog in the right of the rocky area, then bring her over there.
13th girl: Find her in the swamp. She runs off when you talk to her; chase her down. (She stays in the swamp).
You need two kinds of grass. One is in the grassy area, and I think the other is in the desert or rocky area... Mix them up in the kitchen as usual.
14th girl: After a certain amount of time you'll notice food has been going missing. Wait until dark, then find her to the left of your house. Just talk to her.
The boar is in the swamp area. If you just try and catch it, it'll kill you. Get the nuts from the tree near your house first, then catch it and go back to her.
15th girl: After interrogating 14, you hear about her. You can now follow the footsteps leading from your house. They go to a cave in the beach, which you can now enter to find her.
You need two leaves; one from a tree in the desert area, the other from the tree at the right side of the ladder area (down the ladders, then up between two outcrops, guarded by a bear).