I mentioned uncrossing recently (in a patrons-only post) and I've also written about it before on my Patheos blog, but I thought I'd elaborate a bit.
The notion of "crossed conditions" is pretty essential to hoodoo, and it exists in other forms of Southern folk magic even when not described in those terms. The idea is that there's a flow to life, what might otherwise be called your luck, and that it can get blocked up. Doing so will cause trouble for you; unblocking it, if it's blocked, will restore the flow of good things coming your way.
Note that I didn't say anything about what you do or don't deserve. While there's a notion of justice embedded in this kind of magic, and of good and evil, it is also the practice of people who mostly found themselves on the wrong end of racism and poverty, for whom justice was often unavailable and certainly not inevitable. Justice was something you made for yourself, if you got it at all. That can strike people who live in easier circumstances as a bit amoral, but context is crucial to understanding it at all. I don't think you have to be a certain ethnicity or necessarily from the South in order to learn and use conjure, but you do need to be aware that it is part and parcel of a culture (really several overlapping cultures) that includes many things you don't know, and may not know you don't know. If you can't imagine what it's like to fear going to the police, for example, then your mindset may be a little too limited for this kind of work.
You can cross yourself up...with all kinds of things, worry, violating certain kinds of taboos (as a child I was inculcated with a list of things one does and does not do), anger, and so on. Other people might cross you up as well, intentionally or unintentionally. Theologically, the notion of being crossed is very close to the Faery notion of "attachments," "complexes" or "cords": that emotional and energetic entanglements with others can drain you and cause problems. Those blocks and tangles interrupt the natural flow of power and can cause trouble and even illness. They can be created by envy, jealousy, or anger when the feeling is sustained and becomes "stuck" (which usually affects the sender as well). When created on purpose, the method is usually some kind of sticky, tangled, prickly mess (which can also be used as a method of defense, as in the traditional witch bottle full of pins and needles) laid down where the target will step on it or over it, or hidden in their house or yard.
Uncrossing is mainly focused on cleansing and clearing; anything that does that might be put to use, including salt, lemons (or anything lemony), vinegar, ammonia, pine, cedar, rosemary, etc. Other possibilities include rue, pecan shells (specifically for letting go of love), hyssop or poke root. A gentle clearing for bad luck in love could include lavender along with herbs to attract the kind of love you want. This of course should be accompanied by whatever mental and emotional work you need to do to let go of whatever is bothering you; my usual advice is to pay attention to your dreams and write them down, as they will usually offer clues about what is really going on.
The uncrossing spell I gave on my Patheos blog used lemons, salt, and a white candle, but "uncrossing" seven-day candles frequently come in black as well. Here's an alternate approach:
Burn a black candle, surrounded by salt, lemon and rue
Put salt, vinegar, hyssop, rosemary and rue in a bath
Mop your house back to front with lemon, vinegar, hyssop and pine (or make a carpet sprinkle with lemon peel, pine, hyssop and baking soda)
Burn cedar, pine, and myrrh as incense with a white candle
Follow up by carrying some star anise wrapped in a white cloth for protection and luck.
If things don't improve, do a divination (or get a reading from a professional) to see what's going on. I do readings via phone. In general, it's best to start small and work your way up, rather than do big dramatic things first, so do what is simple and see what happens first.