[T-Mobile, Samsung Galaxy SIII] TheLastSidekick:
To the mods, I apologize I seem to have lost my older thread on this matter.. so I will be starting a new thread, with a huge re-write of what I've learned so far on these tweaks.

To anyone who feels the need to raise an objection about of any of the tweaks, I've done a fair amount of research, and if these are placebo I have no idea why they help pamper my device. Please PM me if you have questions, or would like something further explained. That being said, if you've used a ROM released by me and had no problems, and liked it, well these play a role, and it's what I use in ROMs that I use now.

Build.prop tweaks (should be universal but function for devices with high RAM such our S3)

# Performance Tweaks

persist.sys.use_dithering=0 (does not allow device RAM to be freed, we have too much, this isn't needed)

# Calling Tweaks (speeds up ringing to the dialed number)

ro.telephony.call_ring.delay=0

ring.delay=0

# Hardware Tweaks (hardware identification)

com.qc.hardware=true

# Camera Tweaks (tweaks to increase resolution of camera)

ro.media.enc.jpeg.quality=100

ro.media.dec.jpeg.memcap=12000000

ro.media.enc.hprof.vid.bps=12000000

# Battery Tweaks (allows proper sleep mode of the device, dirtyratio specifies how long data is good for before it is overwritten)

ro.ril.disable.power.collapse=1

pm.sleep_mode=1

ro.vold.umsdirtyratio=20

power.saving.mode=1

# Rendering Tweaks (deals with scrolling, screen gestures, redraws, etc)

ro.HOME_APP_ADJ=1

ro.HOME_APP_MEM 2048;

ro.max.fling_velocity=12000

ro.min.fling_velocity=8000

ro.min_pointer_dur=8

persist.sys.scrollingcache=4

persist.sys.smoothscrollbar=true

windowsmgr.max_events_per_sec=150

# Dalvik Tweaks (tweaks to make dalvik and application loading faster)

dalvik.vm.dexopt-flags=v=n,o=v,u=n,m=y

# Data Tweaks (forces DNS to be Google's Primary and Secondary DNS server, specifies packet size for connections)

net.dns1=8.8.8.8

net.dns2=8.8.4.4

net.tcp.buffersize.default=6144,87380,110208,6144,16384,110208

net.tcp.buffersize.wifi=62144,524288,1048576,262144,524288,1048576

net.tcp.buffersize.lte=262144,524288,3145728,262144,524288,3145728

net.tcp.buffersize.hsdpa=6144,262144,1048576,6144,262144,1048576

net.tcp.buffersize.umts=6144,87380,110208,6144,16384,110208

net.tcp.buffersize.hspa=6144,87380,262144,6144,16384,262144

net.tcp.buffersize.gprs=6144,8760,11680,6144,8760,11680

net.tcp.buffersize.edge=6144,26280,35040,6144,16384,35040

# Disable Logging (disables google error reporting, and data reporting (waste of data, waste of battery) )

ro.config.nocheckin=1

profile.force_disable_ulog=1

profiler.force_disable_err_rpt=1

# Call Tweaks (uses higher call quality band)

persist.cust.tel.eons=1

ro.ril.enable.amr.wideband=1

# Misc Tweaks (enables ADB service)

persist.service.adb.enable=1

# Battery Saving Tweaks (increased wifi scanning time for battery saving, handles battery better after disconnections, allows fast dormancy for better battery)

wifi.supplicant_scan_interval=300

ro.mot.eri.losalert.delay=1000

ro.config.hw_fast_dormancy=1

power_supply.wakeup=enable

ro.config.hw_power_saving=1

power.saving.mode=1

# Disable Logcat (disables logcat reports, this is Touchwiz, you shouldn't experience any lockups unless on a custom undervolted kernel)

logcat.live=disable

# Dalvik & Kernel Tweaks (parameters for kernel error checking, and kernel)

debug.performance.tuning=1

ro.kernel.android.checkjni=0

ro.kernel.checkjni=0

dalvik.vm.verify-bytecode=false

dalvik.vm.jmiopts=forcecopy

dalvik.vm.lockprof.threshold=500

# Heapsize Tweaks (heapsize tweaks that specify amount of RAM or memory heapsize is allowed to grow to)

dalvik.vm.heapstartsize=16m

dalvik.vm.heapgrowthlimit=192m

dalvik.vm.heapsize=512m

dalvik.vm.heaptargetutilization=0.75

dalvik.vm.heapminfree=2m

dalvik.vm.heapmaxfree=8m

sysctl.conf tweaks : [requires init.d support, init.d must call sysctl.conf]

#sysctl.conf file

############################

# Battery life tweaks # (decides when the device considers data "dirty" and discards it with newly written information)

############################

sysctl -w vm.dirty_writeback_centisecs=3000;

sysctl -w vm.dirty_expire_centisecs=500;

############################

# kernel tweaks # (handles device scheduler partially, sleeping, and how the kernel handles panics)

############################

sysctl -w kernel.random.read_wakeup_threshold=128

sysctl -w kernel.random.write_wakeup_threshold=256

sysctl -w kernel.threads-max=525810

sysctl -w kernel.sched_compat_yield=1

sysctl -w kernel.panic_on_oops=1

sysctl -w kernel.panic=5

sysctl -w kernel.sched_features=15834233;

sysctl -w kernel.msgmni=2048;

sysctl -w kernel.msgmax=64000;

sysctl -w kernel.shmmax=268435456;

sysctl -w kernel.shmall=2097152;

sysctl -w kernel.sem="500 512000 100 2048";

sysctl -w kernel.hung_task_timeout_secs=0;

sysctl -w kernel.sched_latency_ns=18000000;

sysctl -w kernel.sched_compat_yield=1;

sysctl -w kernel.sched_shares_ratelimit=256000;

sysctl -w kernel.sched_child_runs_first=0;

sysctl -w kernel.threads-max=10000;

sysctl -w kernel.panic=30;

sysctl -w kernel.panic_on_oops=1;

sysctl -w kernel.sched_features=24189;

sysctl -w kernel.sched_min_granularity_ns=1500000;

sysctl -w kernel.sched_wakeup_granularity_ns=3000000;

############################

# CPU tweaks # (adjusts cache queue of CPU)

############################

# Queue size modifications

sysctl -w net.core.optmem_max=20480;

sysctl -w net.unix.max_dgram_qlen=50;

# Net Core Settings

# Location: /proc/sys/net/core

sysctl -w net.core.wmem_max=524288;

sysctl -w net.core.rmem_max=524288;

sysctl -w net.core.rmem_default=256960;

sysctl -w net.core.wmem_default=256960;

############################

# VM & Filesystem tweaks # (specifies amount of virtual RAM, if it should kill a task or not, how often to refer to cache)

############################

sysctl -w fs.lease-break-time=10;

sysctl -w fs.file-max=65536;

sysctl -w fs.inotify.max_queued_events=32000

sysctl -w fs.inotify.max_user_instances=256

sysctl -w fs.inotify.max_user_watches=10240

sysctl -w vm.overcommit_memory=1;

sysctl -w vm.min_free_order_shift=4;

sysctl -w vm.block_dump=0;

sysctl -w vm.oom_dump_tasks=1;

sysctl -w vm.page-cluster=3;

sysctl -w vm.swappiness=0;

sysctl -w vm.dirty_ratio=90;

sysctl -w vm.dirty_background_ratio=80

sysctl -w vm.oom_kill_allocating_task=0

sysctl -w vm.overcommit_memory=1

sysctl -w vm.page-cluster=3

sysctl -w vm.min_free_kbytes=4096

sysctl -w vm.panic_on_oom=0

sysctl -w vm.vfs_cache_pressure=10

sysctl -w vm.min_free_order_shift=4

sysctl -w vm.laptop_mode=0

sysctl -w vm.block_dump=0

############################

# Net Speed tweaks # (hardens you from DDoS and SYN attacks, security orientated may help speed by avoiding unnesscessary data -- unconfirmed)

############################

# UnderUtilized Networking Tweaks below as recommended by avgjoemomma (from XDA)

sysctl -w net.ipv4.tcp_congestion_control=cubic;

# Hardening the TCP/IP stack to SYN attacks

sysctl -w net.ipv4.tcp_syncookies=1;

sysctl -w net.ipv4.conf.all.rp_filter=1;

sysctl -w net.ipv4.conf.default.rp_filter=1;

sysctl -w net.ipv4.tcp_synack_retries=2;

sysctl -w net.ipv4.tcp_syn_retries=2;

sysctl -w net.ipv4.tcp_max_syn_backlog=1024;

sysctl -w net.ipv4.tcp_max_tw_buckets=16384;

sysctl -w net.ipv4.icmp_echo_ignore_all=1;

sysctl -w net.ipv4.icmp_ignore_bogus_error_responses=1;

sysctl -w net.ipv4.tcp_no_metrics_save=1;

sysctl -w net.ipv4.tcp_fin_timeout=15;

sysctl -w net.ipv4.tcp_keepalive_time=1800;

sysctl -w net.ipv4.ip_forward=0;

sysctl -w net.ipv4.tcp_moderate_rcvbuf=1;

sysctl -w net.ipv4.route.flush=1;

sysctl -w net.ipv4.udp_rmem_min=6144;

sysctl -w net.ipv4.udp_wmem_min=6144;

sysctl -w net.ipv4.tcp_rfc1337=1;

sysctl -w net.ipv4.ip_no_pmtu_disc=0;

sysctl -w net.ipv4.tcp_ecn=0;

sysctl -w net.ipv4.tcp_sack=1;

sysctl -w net.ipv4.tcp_fack=1;

# Don't accept source routing

sysctl -w net.ipv4.conf.default.accept_source_route=0 ;

sysctl -w net.ipv4.conf.all.accept_source_route=0;

# Don't accept redirects

sysctl -w net.ipv4.conf.all.accept_redirects=0;

sysctl -w net.ipv4.conf.default.accept_redirects=0;

sysctl -w net.ipv4.conf.all.secure_redirects=0;

sysctl -w net.ipv4.conf.default.secure_redirects=0;

Enabling Sysctl.conf loading from init.d : (copy into file and name whatever you'd like with no extension, place file in init.d folder)

#!/system/bin/sh

# grep sysctl /etc/init.d/*

# Load /sys/etc/sysctl.conf

sysctl -p

To quote our beloved mod [MENTION=3200478]Woody[/MENTION] on some tips for testing / backing up your build.prop :

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Also, [MENTION=4081205]DocHoliday77[/MENTION] gives some advice, if you do not wish to have all tweaks active, or figure out that one isn't doing you justice, but you're just not quite sure yet, add a # in front of that line, it will stop it from activating. "#" in programming terms means comment out, it's usually used to explain something a function, instead of running a command, or a command you want to leave at leisure for your users to run.