My snmpd.conf file from a Slackware 12.0 server, with mrtg working fine.
root@sardela:~# cat /etc/snmp/snmpd.conf
###########################################################################
#
# snmpd.conf
#
# - created by the snmpconf configuration program
#
###########################################################################
# SECTION: System Information Setup
#
# This section defines some of the information reported in
# the "system" mib group in the mibII tree.
# syslocation: The [typically physical] location of the system.
# Note that setting this value here means that when trying to
# perform an snmp SET operation to the sysLocation.0 variable will make
# the agent return the "notWritable" error code. IE, including
# this token in the snmpd.conf file will disable write access to
# the variable.
# arguments: location_string
syslocation "Agia Paraskevi"
# syscontact: The contact information for the administrator
# Note that setting this value here means that when trying to
# perform an snmp SET operation to the sysContact.0 variable will make
# the agent return the "notWritable" error code. IE, including
# this token in the snmpd.conf file will disable write access to
# the variable.
# arguments: contact_string
syscontact "trendy "
# sysservices: The proper value for the sysServices object.
# arguments: sysservices_number
sysservices 78
###########################################################################
# SECTION: Access Control Setup
#
# This section defines who is allowed to talk to your running
# snmp agent.
# rouser: a SNMPv3 read-only user
# arguments: user [noauth|auth|priv] [restriction_oid]
rouser trendy noauth
# rocommunity: a SNMPv1/SNMPv2c read-only access community name
# arguments: community [default|hostname|network/bits] [oid]
rocommunity trendy
# rwcommunity: a SNMPv1/SNMPv2c read-write access community name
# arguments: community [default|hostname|network/bits] [oid]
#rwcommunity trendyrw localhost
###########################################################################
# SECTION: Trap Destinations
#
# Here we define who the agent will send traps to.
# trapcommunity: Default trap sink community to use
# arguments: community-string
trapcommunity public
###########################################################################
# SECTION: Monitor Various Aspects of the Running Host
#
# The following check up on various aspects of a host.
# proc: Check for processes that should be running.
# proc NAME [MAX=0] [MIN=0]
#
# NAME: the name of the process to check for. It must match
# exactly (ie, http will not find httpd processes).
# MAX: the maximum number allowed to be running. Defaults to 0.
# MIN: the minimum number to be running. Defaults to 0.
#
# The results are reported in the prTable section of the UCD-SNMP-MIB tree
# Special Case: When the min and max numbers are both 0, it assumes
# you want a max of infinity and a min of 1.
proc sshd
proc icecast 1 1
proc ntpd 1 1
proc httpd
proc named 1 1
proc dhcpd 1 1
proc squid
# disk: Check for disk space usage of a partition.
# The agent can check the amount of available disk space, and make
# sure it is above a set limit.
#
# disk PATH [MIN=100000]
#
# PATH: mount path to the disk in question.
# MIN: Disks with space below this value will have the Mib's errorFlag set.
# Can be a raw byte value or a percentage followed by the %
# symbol. Default value = 100000.
#
# The results are reported in the dskTable section of the UCD-SNMP-MIB tree
disk / 100000000
disk /spare/storage1 100000000
disk /spare/storage2 100000000
disk /spare/storage3 100000000
disk /spare/storage4 100000000
disk /spare/storage5 100000000
disk /var/squid 10000000
disk /var/squid/cache1 10000000
disk /var/squid/cache2 10000000
disk /var/squid/cache3 10000000
# load: Check for unreasonable load average values.
# Watch the load average levels on the machine.
#
# load [1MAX=12.0] [5MAX=12.0] [15MAX=12.0]
#
# 1MAX: If the 1 minute load average is above this limit at query
# time, the errorFlag will be set.
# 5MAX: Similar, but for 5 min average.
# 15MAX: Similar, but for 15 min average.
#
# The results are reported in the laTable section of the UCD-SNMP-MIB tree
load 75.0 65.0 50.0
###########################################################################
# SECTION: Extending the Agent
#
# You can extend the snmp agent to have it return information
# that you yourself define.
# pass: Run a command that intepretes the request for an entire tree.
# The pass program defined here will get called for all
# requests below a certain point in the mib tree. It is then
# responsible for returning the right data beyond that point.
#
# arguments: miboid program
#
# example: pass .1.3.6.1.4.1.2021.255 /path/to/local/passtest
#
# See the snmpd.conf manual page for further information.
#
# Consider using "pass_persist" for a performance increase.
pass .1.3.6.1.4.1.4413.4.1 /usr/bin/ucd5820statOf course many of these things are not necessary as they monitor disk space, processes active but in general having a contact name, system location, rouser and rocommunity should do the job.