Here are some tips for a Cockney accent. Now, this is a very general form of your very urban London accent. So you want to bring your lips really far forward for the oral posture. And you want to almost imagine that there's like a light bulb in your mouth, so there's a lot of space in the back of your mouth and the front of your mouth is closed. Bring your lip corners forward, for something that looks like this.
Let us look at some sound changes for Cockney. The 'E' turns into an 'eh'. "Does she really need to make believe she can't see me?" in your Cockney accent turns into, "Does she really need to make believe she can't see me?" "Eh, eh, eh." So it is that gentle up-glide into the 'e' sound.
Another important one is that 'ah to o.' Now, "Saul's daughter studied law" is how I would say it in my American accent. In RP we'd bring our lips corners forward for, "Saul's daughter studied law." But for Cockney you want to just shove those lip corners all the way forward and go, "Saul's daughter studied law." The more forward you can bring your lip corners, the easier all of the other sound changes are to make. So, "Saul's daughter studied law. Saul's daughter studied law." Hear that? So in RP, we would bring that 'e' sound to an 'ih' in cases like, "Betty is really silly. Betty is really silly." But in Cockney, it actually is closer to your American pronunciation of 'e', "Betty is really silly. Betty is really silly." You go all the way to the 'e' sound. But notice that glottal stop on the word, "Betty. Betty?" There are a lot of glottals in Cockney accent and that's part of the musicality of the accent. A lot of glottal stops, a lot of syncopation.
A couple more sound changes for Cockney. Tat 't-h' sound "th" turns into an "f" sometimes, it turns into an 'f' sometimes. "I knew I'd think of something." turns into, "I knew I'd think of something. I knew I'd think of something. I knew I'd think of something." And, you know, you go all the way into a sound change like that, then you kind of back off from it once you get it because it sounds a little strong at first and then when you practice them and drill them, you knock it back a little bit and it sounds a little more authentic.
The 't-h' sound can also turn into a 'v' sound as in, "My brother and I are always together. My brother and I are always together." turns into "brother, together." You hear the elision, just like in the RP and the Estuary accent. "My brother and I. Brother and I. Brother and I are always together," so you hear that elision of the 'r' sound too.
So again, listen to some native speakers for that musicality. It's a syncopated sound. It's a really urban sound so those sounds are very far forward and a little sharper than you would get in your more upper class British accent where it's a more little delicate. And so then you can hear some differences for yourself, okay?
There are some tips for a general Cockney accent.