There are recommendations about getting your ex back that I disagree with. Some of the ways that are being recommended work in the short term but in building a long term relationship they will not work. I'd like to review some of these and what the problems are with these approaches.
1. Flirt with everyone when in the presence of your ex. I'm not talking about casual contact with the opposite sex but straight flirting. If you want to have a long term relationship with your ex then trust will be a large part of it. Your ex will always start questioning your behavior when they're not around. If they remember this flirting when they were in the room, even if you were not together, then they are going to ever question your behavior when they're not around. Not what I would consider a building block towards a long term relationship.
2. Acting any way that is not consistent with the person you normally are. Being the life of the party if that's not the normal you. Your ex knows what he perceives to be the real you. Anything that is not consistent with that will make him wonder who is the real you. Is it the way that you're doing now or the way you are when you're around him? If you want to get back together just try to be the person they started the relationship with in the first place.
3. Building a relationship with someone who is close to your ex just as a means of spying on them. Although this is very tempting as a way to keep track of your ex, when you get back together they will question what your real intentions were. It also will not make you look very good to the person you started the relationship with and if they are close to your ex they may not like you too much. You will need all of your ex's friends support you can get when you get back together.
4. Certainly do not date any friend of your ex's. If you want a way to diminish your trustworthiness when you get back together this is one of the quickest ways. This will come back to haunt you for ever. This will hurt your chances of having a long term relationship to the point that it may not be able to recover from it.
5. Dating someone that is an adversary of your ex's. After dating someone whom your ex perceives as a threat may make them take the approach that they do not want you back. Not because you're a different person but because of where you've been.
As you can see some of these things can be effective in creating a response from your ex. But you may not get the response you want. They may be counter productive in the long run. If you really want your ex back, take some time to reflect on the relationship, and then develop a plan that will be effective in the long run.