[Galaxy S I9000 General] erpurohit:
After being on custom roms around 2 years and flashing of roms more than hundreds of time I am sharing my experience on saving battery / smoothness / faster rom so if you dont agree or have any issue give me a PM and if I like your suggestion then will include in the OP with proper credits.

These are not all founded by me I have got the base from Jarmezrocks (A big thanks to him).

Recommended applications:

* Autostarts - this application is a paid app and worth it's weight in gold

* Juice defender - this app is one of the best on the market (I dont use it but have heard that its good by user so it is included)

* Titanium backup - (I would suugest to buy the pro version for the batch opperation and few more options)

Which roms I use?

1.	Remic-JB

2.	X-Bean

3.	Mackay Rom

Which kernels? anyone of semaphore/devil/mackay i keep moving in between them.

Steps for flashing a a new rom / update of the rom you are using:

1.	take full backup using TB by selecting 'backup all user app + system data

2.	Reboot phone in recovery

3.	wipe user data / factory reset

4.	wipe cache partition

5.	wipe dalvik cache

6.	format system under mounts and storage

7.	flash the rom and gapps (if dev has ask to flash gapps seprately)

8.	reboot and loged in use your login credentials

9.	let the phone settle down for around 10-15 mins

10.	Load titanium and go to menu -> batch -> restore -> Restore all apps with data -> Run

11.	Inside this sub menu click on 'deselect all'

12.	Check the toggle 'data only' (this is the restore for system apps that you use and have stored settings or info i.e. Mms and settings and what ever)*note these apps will be marked with green text in the list or maybe red....try not to restore data for apps marked with red text unless you are absolutely certain that your settings are necessary. (*try not to restore your user accounts this way, sign into your Google account is best practice*to backup contacts and sms/mms use TB)

13.	click the top button 'Run the batch operation'

14.	Once completed return to the same menu again -> batch -> restore -> Restore user apps with data -> Run

15.	Inside this sub menu click on 'deselect all'

16.	Check the toggle 'App+Data' (you should do this for user apps only; try to restore data for only those apps for whome you need the data back like games, dont do for facebook, and such apps if you can avoid).

17.	click the top button 'Run the batch operation'

18.	Reboot into recovery and then delete dalvik and wipe caches and reset permissions

This way will gives you a fresh rom always to use with no traces of issue from previous.

Warning:- I use the above steps and will help you to my extent if you falls in any issue however I am not responsible if you burn/broken your device.

Modems

Choosing the correct modem.bin file to flash that is relevant to your device, your service provider and your region can have a huge impact on performance. And even if it doesn't you can make it have a huge impact on performance!

A great choice of modem could enable any user to reduce their wifi.supplicant_scan_interval from one value to an even lower rate. NOTE: The larger the number the better! (you can get all the modems from here).

The longer the period of time between subsequent wifi scans the less amount of battery you are going to use..

Note also that adjusting this value could improve or worsen your wifi signal and maintained strength and connection. Do so wisely.

Likewise that if you have great battery consumption yet you have faulty connection (if any?) then this can be remedied by either adjusting the scan rate (scan interval) to combat the issue. Compensating too much in either direction (for connectivity or for battery performance) may flag a need to change modems to something more suitable? View here for detailed example

....still incomplete and lots more to come...wait....:)