If you are going to go out of your way to kill a stranger, it should be a woman. That way, you can rape and/or sodomize her before or after the murder.
Picking the right woman will be kinda hard. You definately don't want a woman with kids. Too loose to get rocks off properly. Although, if you are into object rape, the streched opening can really take some big stuff without tearing.
A virgin would be a bad choice too. They probably won't move right when you start and will get you all bloddy. If you insist on a virgin, might as well get a young one. After all, if you are caught, what's a little molestation charge on top of the murder rap. 14 to 16 would probably be the best bet for virgins.
Really what you are looking for is a newlywed couple. Maybe up to the 4-month point. She'll be fully primed for pumping and will move with you if for nothing else than to avoid the pain. She'll probably have nice undies on which can be an added bonus.
To make it even sweeter, her hubby will be devistated for life. It's like destroying two lives for the price of one.
Or just kill the hubby too. Disable him first so that he can witness the raping. Maybe blind him or break his arms and legs. Cut his trousers open so she can see him get hard as he hears her being penetrated.
You can probably make her cum. Her body's reaction is completely seperate from her heart's intentions. With the right motion and attention to detail, she'll die feeling she's betrayed her true love by spending the last minutes of her life orgasming on another man's love tool.
Now the sticky part: disposal. You can't get rid of her right away. Your evidince is all inside her. You need to give her body time to rid itself of your seed. Maybe a week or so. Break her jaw and then tape it shut to keep her quiet if noise is a problem. The hard part will be to keep from raping her agian and agian.
If she gets pregnant, best to rent a boat and send her to the bottom. Cut her into small peices and spread the love. Synthetic pillowcases weighted with rocks and secured with wire are perfect for disposing of body parts.
You also need lots of practice.
Practice killing animals often. Buy a cat. Keep it for a few weeks. Feed it and love it. Then kill it. Record your heartrate after. Keep doing that till you can kill an animal you have kept for a few months with no reaction. Try torturing it first. If you get excited, you will make a mistake. Use the corpses for disposal training.
Also get some larger animals. Big dogs and the like. Cut them up to see how long it takes and what tools you need. Practice dislocating joints and cutting them free. It's a lot easier than trying to hack through a femur.
Talk to women a lot. Everywhere. Any woman you see, talk to her. Tell her intimate things. Just tell a mom in the supermarket what a nice ass she has. Tell the girl in the checkout line how nice her hair smells. Ask her about her perfume. Randomly tell a mom you'd like to jack off on her tits while her husband pumps her wet cunt.
Once you can do that without too much adreneline, go further. Ask women in random places for sex. Try touching women in public. You want to be able to seize the moment without any rush. If you are high on adreneline, you will make a mistake.
Make sure your practice is far away. Seperating it by several years would be nice. Wear a disguise.
Very few people start on murder, so try some petty crime first. Go for low-risk stuff like car theft and/or rob a convenience store. Maybe pickpocket or assault someone.
Remember that there is a balance between getting away and not. You need practice, but too much petty crime will get you caught. Then you are fucked for getting away with murder. But without the practice, you'll hesitate at the moment of truth or make a mistake.