Here's something I posted on 2p2 regarding staking.  I'll look at refining it for a full article since it seems to be a popular subject.
 
 
Depends to be honest.

A few factors to consider:

Trust/honesty - I've passed up on a stake from someone I consider to be a top 10-20 husng player because I didn't trust them. No amount of skill can counteract a lack of trust. If you can't trust the person, don't even bother considering anything else. And the better the deal sounds, the more likely it is a scam in my experience when you have a lack of trust.

This works two ways, always be up front and honest with the person you are staking. If you deceive, lie or change rules, don't be surprised when they do the same.

Skill and Length - First, determine what kind of skills they have. If they've only proven to beat the 55s for a few ROI or they beat the 33s for 5% but are beating the 55s for 10% with a super small sample, it's probably not a good idea to throw this person into the 110-220s right away. If you feel you are more than qualified to judge this (I feel like I can judge a lot of husng player's skills, but when it comes to other games I am must more wary on who I stake bc I know it's much harder for me to tell when they are playing badly) then obviously you can be more precise, otherwise you rely mostly on hard statistical facts.

Length really has to do with skill. If somebody wins 100% of games you hold no risk, so you can stake them for 1-infinite games and it's profitable. However, if you stake somebody with a 55% winrate for 2 games, it's not going to be profitable. You're putting up the money for usually 40-75% of their profits, the longer the deal the better it is for you. There are formulas for this kind of stuff, pay a math person to figure it out for you if you're really interested.

Rules - Require accountability on the stakee's part. Two way access to a new email address linked to the poker account is a must in many cases. Contracts can be good, but be weary if you're dealing with people in different countries. I usually require ID, a phone # and a few other things from stakees. If they can't provide me their personal information, why should I bother sending them hundreds of dollars?

Make sure you manually check HHs from the poker site. Sharkscope is a great tool to get an idea of how things are going, but Sharkscope is not 100% accurate.

Make sure the stakee isn't losing massive amounts of money to a single person. Many a stakee have chip dumped a lot of their profit to a "friend" in order to make more money on a stake.

Even contact the poker site to let them know you'll be staking player xxx. If both people email them, it may not give you any special rules or stop the stakee from scamming you, but at least the poker site is aware in advance what is going on and if there is some sort of dispute it can lend to your credibility.

Saying NO - A lot of people laugh at this, but it's nothing to scoff at. Just read Primo's thread about being scammed if you question this part.

While his case is an extreme example, even the most careful of us have lost money to scammers or dishonest people on stakes or borrowed money. If something isn't right or you don't want to do something, just say no. This goes along with most things in life. It does baffle me when people complain to me "god I got scammed by a transfer I did with someone" "why'd you do it?" "the guy was nice, I wanted to help him out." If you want to help somebody, go volunteer for the needy, help a family member out with something difficult. Think about what you're doing... sending money to a stranger over the internet to help him gamble (I use the term gamble bc the players that are skillful and profitable are usually the last people to ask for help from a stranger). This isn't really helping anybody in the true sense of helping and you're just exposing yourself to risk.

Exposure - This is the last thing off the top of my head for staking. I used to give people 20+ buyins for a stake. Why? So they can feel comfortable with money in their account? It's a stake and giving more money than necessary to a stakee is just going to expose you to a lot more risk.

Giving a stakee 5-10 buyins at a time is much more rewarding. First, if you get scammed you lose less money. Second, if the stakee has a tilting session (even the best players do), you can only lose 5-10 tilted buyins rather than 20+ buyins. 5 buyin tilt sessions every so often can be overcome, 20+ buyin tilt sessions are devastating. This includes profits too. Just be aware it's a lot harder to convince a stakee that it's in their best interests to send you all profits and to keep x buyins in their account at all times and not go above that. Most people have a tough enough time playing with 5-10 buyins of your own money in their account and prefer "20+." Just assure them that you'll replenish it as long as the rules of the stake are followed, and not to worry about busting the money due to variance.

In the end, staking is almost always about making money for yourself, whichever end you're on. If something is threatening that aspect of the stake, ask a friend. It's much easier to objectively analyze a stake you're not a part of than to make the decision in real time. It took me over a half dozen stakes to figure this stuff out, and I wasn't alone. Many players have helped me refine my opinion of how stakes should work out, none more than Skates.

In general, if you're playing SNGs (where rakeback is a huge part of your profit), rakeback should be included in the splits.  50/50 is fine for a percentage, but it really depends on how many games you play in a "month".  The stake should be based on the number of games played, not amount of time played.
I DO NOT recommend staking between friends unless there is a huge gap in the utility value of the money (ie, say if I were to stake a friends in $22s while simultaneously playing $570s).  Staking should be rigorous and a business decision; try to keep friends out of it.  If it's hard to discuss it, you should go another direction and find another backer.  That said, I've had staking deals work between friends before.