Assuming you are trying to get the generic harem (i.e. tomboy, tsundere, loli,,imouto, kuudere, senpai)
-If you are an average human with generic feats, get a perv best friend/ wing man, he will introduce you to the potential harem
-Live alone, you can activate potential flags with the whole home alone setting (study date, rain event, cooking)
-As other users have stated, be as dense and clumsy as possible. (Fall onto them with revealing positions)

-If you want lure a specific types one by one follow these steps

Tomboy - They most likely plays a sport, ask them to teach you or introduce yourself as a major fan of the
sport (or them). Attempt the sport to impress her, fail horribly to show her how hard you are trying.
Compliment them in a dense/oblivious manner. If she tries to change herself remind her how much you like
their current self.She should confess her love. -You have acquired the Tomboy.-

Tsundere - You most likely will meet them first at the start. Bump into them giving you the ("I see your panties")
flag. They will most likely call you a pervert (You have created a lasting impression). Help her out with things for no
reason. Keep a mysterious persona. While helping her if she does something normal/cute compliment her with an
innocent compliment. Repeat steps. Helps with flags("its raining really hard my place is close", " can you please help
me study", "I need love advice"). Love confession should follow. -You have acquired the Tsundere-

Kuudere - Most likely found in the library or club like literature. Use a warm friendly persona. Show an interest in
their hobbies("what are you reading?" "Wow you're really good"). Be bad at a subject they are strong in. Ask them to
help you study (This flag is usually fool proof) . Be really determined and study hard in front of them. When you get a
good grade on the test show them and thank them in earnest ( with a smile and blush preferably). Invite her places
like the amusement park. Have her show various sides of herself and show her how much you enjoy being with her.
Silent love confession should follow. -You have acquired the Kuudere-

Loli - kidnap her from her evil kidnappers and pretend to be her savior. Stockholm will kick in. Or adopt one and
have her acknowledge you as "onii-chan". Give her lots of candy and gifts. -You have acquired a Loli ?-

Senpai / Older girl - a responsible kohai that looks up to her. Use a persona similar to what was used for the
Tomboy type.If Senpai is in a sport support her. Heres where perverted wingman steps in. He will set you up with
Senpai. Run into Senpai after getting groceries and ask her to stay for dinner since you live alone.It will show Senpai
how mature you are. Straightforwardly ask senpai on a date(go to movies if she accepts) and if she rejects ask ("
how can I get you to see me as a man"*or woman). She will give you seemingly impossible task. Complete them
all. People will begin to taunt you for being like a servant. Senpai will get mad at the rumors and ask you why you'd
do this for her. Explain in earnest how much you love Senpai. Confession/Acceptance will follow.
-You have aquired Senpai-

*Breast size for types will differ.
Thats pretty much it, I do believe that I explained imouto to you before.
Good luck with creating your harem Senpai!